py, mk: Revert change where build variables set with ?=.
py, mk: Revert change where build variables set with ?=.

?= operator does not do delayed expansion (unlike =).

praemdonck/micropython,ryannathans/micropython,kerneltask/micropython,EcmaXp/micropython,ruffy91/micropython,SHA2017-badge/micropython-esp32,jmarcelino/pycom-micropython,danicampora/micropython,xyb/micropython,dinau/micropython,omtinez/micropython,bvernoux/micropython,HenrikSolver/micropython,jlillest/micropython,ruffy91/micropython,pozetroninc/micropython,toolmacher/micropython,suda/micropython,ganshun666/micropython,swegener/micropython,heisewangluo/micropython,TDAbboud/micropython,kerneltask/micropython,ruffy91/micropython,MrSurly/micropython-esp32,mhoffma/micropython,dxxb/micropython,swegener/micropython,hosaka/micropython,vriera/micropython,chrisdearman/micropython,xhat/micropython,tuc-osg/micropython,noahwilliamsson/micropython,TDAbboud/micropython,kostyll/micropython,slzatz/micropython,galenhz/micropython,MrSurly/micropython-esp32,torwag/micropython,lbattraw/micropython,SHA2017-badge/micropython-esp32,Timmenem/micropython,puuu/micropython,dxxb/micropython,slzatz/micropython,mgyenik/micropython,vriera/micropython,infinnovation/micropython,noahwilliamsson/micropython,MrSurly/micropython,oopy/micropython,pramasoul/micropython,kostyll/micropython,tdautc19841202/micropython,TDAbboud/micropython,ChuckM/micropython,xhat/micropython,cwyark/micropython,deshipu/micropython,hosaka/micropython,adamkh/micropython,TDAbboud/micropython,swegener/micropython,kostyll/micropython,methoxid/micropystat,lbattraw/micropython,alex-robbins/micropython,ganshun666/micropython,pfalcon/micropython,deshipu/micropython,blazewicz/micropython,dxxb/micropython,Peetz0r/micropython-esp32,skybird6672/micropython,ryannathans/micropython,hosaka/micropython,adafruit/micropython,deshipu/micropython,praemdonck/micropython,redbear/micropython,orionrobots/micropython,omtinez/micropython,adamkh/micropython,blmorris/micropython,xyb/micropython,paul-xxx/micropython,xhat/micropython,drrk/micropython,ericsnowcurrently/micropython,chrisdearman/micropython,cloudformdesign/micropython,feilongfl/micropython,noahchense/micropython,pramasoul/micropython,adafruit/circuitpython,alex-robbins/micropython,HenrikSolver/micropython,misterdanb/micropython,jlillest/micropython,jimkmc/micropython,trezor/micropython,alex-march/micropython,cnoviello/micropython,adamkh/micropython,infinnovation/micropython,hosaka/micropython,Timmenem/micropython,jlillest/micropython,suda/micropython,neilh10/micropython,firstval/micropython,pfalcon/micropython,alex-march/micropython,aethaniel/micropython,alex-march/micropython,utopiaprince/micropython,Vogtinator/micropython,methoxid/micropystat,rubencabrera/micropython,drrk/micropython,turbinenreiter/micropython,mhoffma/micropython,xuxiaoxin/micropython,ChuckM/micropython,mianos/micropython,tdautc19841202/micropython,KISSMonX/micropython,noahchense/micropython,adafruit/circuitpython,emfcamp/micropython,Peetz0r/micropython-esp32,drrk/micropython,jmarcelino/pycom-micropython,pfalcon/micropython,blazewicz/micropython,blazewicz/micropython,matthewelse/micropython,firstval/micropython,skybird6672/micropython,dmazzella/micropython,galenhz/micropython,cwyark/micropython,hiway/micropython,ericsnowcurrently/micropython,selste/micropython,omtinez/micropython,jlillest/micropython,SungEun-Steve-Kim/test-mp,lbattraw/micropython,ericsnowcurrently/micropython,adafruit/circuitpython,SungEun-Steve-Kim/test-mp,alex-robbins/micropython,Vogtinator/micropython,ryannathans/micropython,AriZuu/micropython,ganshun666/micropython,hiway/micropython,slzatz/micropython,trezor/micropython,galenhz/micropython,toolmacher/micropython,redbear/micropython,noahwilliamsson/micropython,Timmenem/micropython,neilh10/micropython,firstval/micropython,mpalomer/micropython,misterdanb/micropython,ChuckM/micropython,EcmaXp/micropython,dinau/micropython,vriera/micropython,suda/micropython,infinnovation/micropython,turbinenreiter/micropython,blazewicz/micropython,ryannathans/micropython,xyb/micropython,ernesto-g/micropython,firstval/micropython,slzatz/micropython,EcmaXp/micropython,SungEun-Steve-Kim/test-mp,orionrobots/micropython,SungEun-Steve-Kim/test-mp,HenrikSolver/micropython,blmorris/micropython,heisewangluo/micropython,vitiral/micropython,emfcamp/micropython,KISSMonX/micropython,mgyenik/micropython,torwag/micropython,hiway/micropython,Timmenem/micropython,aethaniel/micropython,adafruit/micropython,pfalcon/micropython,oopy/micropython,ericsnowcurrently/micropython,paul-xxx/micropython,dxxb/micropython,warner83/micropython,stonegithubs/micropython,matthewelse/micropython,ahotam/micropython,xuxiaoxin/micropython,ahotam/micropython,PappaPeppar/micropython,aethaniel/micropython,dmazzella/micropython,vitiral/micropython,chrisdearman/micropython,trezor/micropython,ceramos/micropython,trezor/micropython,tralamazza/micropython,tuc-osg/micropython,micropython/micropython-esp32,henriknelson/micropython,matthewelse/micropython,cwyark/micropython,utopiaprince/micropython,pramasoul/micropython,aethaniel/micropython,stonegithubs/micropython,rubencabrera/micropython,mianos/micropython,KISSMonX/micropython,blmorris/micropython,ganshun666/micropython,ganshun666/micropython,misterdanb/micropython,aethaniel/micropython,Vogtinator/micropython,puuu/micropython,methoxid/micropystat,stonegithubs/micropython,dinau/micropython,cwyark/micropython,henriknelson/micropython,turbinenreiter/micropython,mgyenik/micropython,neilh10/micropython,MrSurly/micropython,kostyll/micropython,vitiral/micropython,drrk/micropython,skybird6672/micropython,blmorris/micropython,stonegithubs/micropython,henriknelson/micropython,adafruit/circuitpython,blmorris/micropython,torwag/micropython,SHA2017-badge/micropython-esp32,ernesto-g/micropython,warner83/micropython,supergis/micropython,redbear/micropython,ceramos/micropython,drrk/micropython,ryannathans/micropython,adamkh/micropython,tuc-osg/micropython,AriZuu/micropython,tobbad/micropython,orionrobots/micropython,noahchense/micropython,PappaPeppar/micropython,selste/micropython,xhat/micropython,Peetz0r/micropython-esp32,mgyenik/micropython,noahwilliamsson/micropython,dxxb/micropython,lbattraw/micropython,dhylands/micropython,micropython/micropython-esp32,EcmaXp/micropython,danicampora/micropython,praemdonck/micropython,lowRISC/micropython,micropython/micropython-esp32,dmazzella/micropython,AriZuu/micropython,bvernoux/micropython,selste/micropython,ChuckM/micropython,adafruit/circuitpython,MrSurly/micropython-esp32,methoxid/micropystat,pozetroninc/micropython,feilongfl/micropython,xyb/micropython,Peetz0r/micropython-esp32,mianos/micropython,Timmenem/micropython,omtinez/micropython,suda/micropython,tobbad/micropython,pfalcon/micropython,emfcamp/micropython,puuu/micropython,chrisdearman/micropython,PappaPeppar/micropython,hiway/micropython,heisewangluo/micropython,MrSurly/micropython,swegener/micropython,xuxiaoxin/micropython,alex-robbins/micropython,heisewangluo/micropython,Vogtinator/micropython,danicampora/micropython,dhylands/micropython,bvernoux/micropython,puuu/micropython,suda/micropython,heisewangluo/micropython,stonegithubs/micropython,toolmacher/micropython,cnoviello/micropython,tuc-osg/micropython,adafruit/micropython,cloudformdesign/micropython,tdautc19841202/micropython,dhylands/micropython,lowRISC/micropython,warner83/micropython,skybird6672/micropython,deshipu/micropython,mgyenik/micropython,dmazzella/micropython,dhylands/micropython,ericsnowcurrently/micropython,supergis/micropython,tralamazza/micropython,oopy/micropython,mpalomer/micropython,supergis/micropython,SungEun-Steve-Kim/test-mp,turbinenreiter/micropython,redbear/micropython,matthewelse/micropython,selste/micropython,puuu/micropython,micropython/micropython-esp32,ahotam/micropython,kerneltask/micropython,methoxid/micropystat,mpalomer/micropython,feilongfl/micropython,martinribelotta/micropython,selste/micropython,orionrobots/micropython,pozetroninc/micropython,matthewelse/micropython,emfcamp/micropython,mpalomer/micropython,oopy/micropython,Vogtinator/micropython,henriknelson/micropython,pozetroninc/micropython,slzatz/micropython,henriknelson/micropython,cwyark/micropython,tdautc19841202/micropython,omtinez/micropython,skybird6672/micropython,bvernoux/micropython,danicampora/micropython,cnoviello/micropython,orionrobots/micropython,jimkmc/micropython,oopy/micropython,vriera/micropython,cloudformdesign/micropython,chrisdearman/micropython,ruffy91/micropython,cnoviello/micropython,xhat/micropython,misterdanb/micropython,xyb/micropython,jimkmc/micropython,turbinenreiter/micropython,mianos/micropython,tralamazza/micropython,dhylands/micropython,jimkmc/micropython,tdautc19841202/micropython,EcmaXp/micropython,martinribelotta/micropython,pramasoul/micropython,xuxiaoxin/micropython,ceramos/micropython,redbear/micropython,ceramos/micropython,HenrikSolver/micropython,xuxiaoxin/micropython,mhoffma/micropython,feilongfl/micropython,tuc-osg/micropython,lowRISC/micropython,tobbad/micropython,PappaPeppar/micropython,hosaka/micropython,ernesto-g/micropython,tralamazza/micropython,AriZuu/micropython,misterdanb/micropython,MrSurly/micropython-esp32,dinau/micropython,adamkh/micropython,blazewicz/micropython,jmarcelino/pycom-micropython,jmarcelino/pycom-micropython,micropython/micropython-esp32,utopiaprince/micropython,torwag/micropython,cnoviello/micropython,noahchense/micropython,supergis/micropython,supergis/micropython,alex-march/micropython,alex-robbins/micropython,ruffy91/micropython,paul-xxx/micropython,KISSMonX/micropython,praemdonck/micropython,SHA2017-badge/micropython-esp32,mpalomer/micropython,tobbad/micropython,ChuckM/micropython,noahwilliamsson/micropython,cloudformdesign/micropython,adafruit/micropython,bvernoux/micropython,HenrikSolver/micropython,galenhz/micropython,martinribelotta/micropython,tobbad/micropython,infinnovation/micropython,paul-xxx/micropython,rubencabrera/micropython,warner83/micropython,hiway/micropython,dinau/micropython,mhoffma/micropython,neilh10/micropython,mhoffma/micropython,galenhz/micropython,kostyll/micropython,KISSMonX/micropython,trezor/micropython,swegener/micropython,pramasoul/micropython,jmarcelino/pycom-micropython,praemdonck/micropython,SHA2017-badge/micropython-esp32,vitiral/micropython,paul-xxx/micropython,MrSurly/micropython,warner83/micropython,lowRISC/micropython,firstval/micropython,danicampora/micropython,matthewelse/micropython,kerneltask/micropython,Peetz0r/micropython-esp32,toolmacher/micropython,alex-march/micropython,AriZuu/micropython,jimkmc/micropython,utopiaprince/micropython,mianos/micropython,martinribelotta/micropython,TDAbboud/micropython,ernesto-g/micropython,PappaPeppar/micropython,toolmacher/micropython,vitiral/micropython,utopiaprince/micropython,ahotam/micropython,torwag/micropython,kerneltask/micropython,ceramos/micropython,infinnovation/micropython,deshipu/micropython,rubencabrera/micropython,noahchense/micropython,rubencabrera/micropython,lowRISC/micropython,emfcamp/micropython,cloudformdesign/micropython,adafruit/circuitpython,lbattraw/micropython,feilongfl/micropython,ernesto-g/micropython,martinribelotta/micropython,pozetroninc/micropython,jlillest/micropython,ahotam/micropython,adafruit/micropython,vriera/micropython,MrSurly/micropython,neilh10/micropython,MrSurly/micropython-esp32