mpy-cross: Fix compiler detection for including windows/fmode.c
mpy-cross: Fix compiler detection for including windows/fmode.c

fmode.c should only be included for builds targetting 'pure' windows, i.e.
msvc or mingw builds but not when using msys or cygwin's gcc (see #2298).
Just checking if the OS is windows and UNAME doesn't have msys stil leaves
the gate open for builds with cygwin's gcc since UNAME there is e.g.
CYGWIN_NT-6.1-WOW.
Fix this by checking for 'mingw' explicitly in the compiler version; both
gcc and clang have the -dumpmachine flag so the check should be ok for
all platforms.

adafruit/micropython,cwyark/micropython,AriZuu/micropython,Timmenem/micropython,ryannathans/micropython,toolmacher/micropython,puuu/micropython,henriknelson/micropython,kerneltask/micropython,deshipu/micropython,adafruit/circuitpython,AriZuu/micropython,HenrikSolver/micropython,puuu/micropython,pfalcon/micropython,bvernoux/micropython,TDAbboud/micropython,AriZuu/micropython,trezor/micropython,pozetroninc/micropython,adafruit/micropython,blazewicz/micropython,adafruit/circuitpython,pfalcon/micropython,oopy/micropython,ryannathans/micropython,chrisdearman/micropython,infinnovation/micropython,dmazzella/micropython,tobbad/micropython,bvernoux/micropython,PappaPeppar/micropython,bvernoux/micropython,selste/micropython,lowRISC/micropython,HenrikSolver/micropython,hiway/micropython,MrSurly/micropython,infinnovation/micropython,deshipu/micropython,torwag/micropython,dmazzella/micropython,oopy/micropython,pramasoul/micropython,pfalcon/micropython,tobbad/micropython,lowRISC/micropython,MrSurly/micropython,AriZuu/micropython,torwag/micropython,pozetroninc/micropython,henriknelson/micropython,infinnovation/micropython,toolmacher/micropython,lowRISC/micropython,adafruit/circuitpython,tralamazza/micropython,pramasoul/micropython,micropython/micropython-esp32,swegener/micropython,henriknelson/micropython,pramasoul/micropython,bvernoux/micropython,alex-robbins/micropython,swegener/micropython,blazewicz/micropython,micropython/micropython-esp32,ryannathans/micropython,pramasoul/micropython,deshipu/micropython,micropython/micropython-esp32,cwyark/micropython,dmazzella/micropython,cwyark/micropython,swegener/micropython,Timmenem/micropython,pozetroninc/micropython,trezor/micropython,torwag/micropython,SHA2017-badge/micropython-esp32,PappaPeppar/micropython,kerneltask/micropython,puuu/micropython,adafruit/micropython,Timmenem/micropython,torwag/micropython,infinnovation/micropython,pfalcon/micropython,HenrikSolver/micropython,ryannathans/micropython,toolmacher/micropython,chrisdearman/micropython,selste/micropython,kerneltask/micropython,HenrikSolver/micropython,TDAbboud/micropython,TDAbboud/micropython,adafruit/micropython,MrSurly/micropython,tobbad/micropython,trezor/micropython,MrSurly/micropython-esp32,deshipu/micropython,selste/micropython,alex-robbins/micropython,trezor/micropython,trezor/micropython,oopy/micropython,SHA2017-badge/micropython-esp32,SHA2017-badge/micropython-esp32,swegener/micropython,tralamazza/micropython,PappaPeppar/micropython,torwag/micropython,chrisdearman/micropython,tralamazza/micropython,adafruit/circuitpython,adafruit/circuitpython,micropython/micropython-esp32,hiway/micropython,lowRISC/micropython,bvernoux/micropython,oopy/micropython,adafruit/circuitpython,SHA2017-badge/micropython-esp32,selste/micropython,HenrikSolver/micropython,dmazzella/micropython,ryannathans/micropython,tralamazza/micropython,Timmenem/micropython,puuu/micropython,hiway/micropython,selste/micropython,tobbad/micropython,infinnovation/micropython,pozetroninc/micropython,blazewicz/micropython,tobbad/micropython,henriknelson/micropython,henriknelson/micropython,pfalcon/micropython,toolmacher/micropython,hiway/micropython,kerneltask/micropython,oopy/micropython,blazewicz/micropython,swegener/micropython,lowRISC/micropython,deshipu/micropython,micropython/micropython-esp32,MrSurly/micropython,MrSurly/micropython-esp32,blazewicz/micropython,TDAbboud/micropython,hiway/micropython,toolmacher/micropython,alex-robbins/micropython,PappaPeppar/micropython,SHA2017-badge/micropython-esp32,kerneltask/micropython,adafruit/micropython,MrSurly/micropython-esp32,AriZuu/micropython,chrisdearman/micropython,cwyark/micropython,TDAbboud/micropython,cwyark/micropython,chrisdearman/micropython,alex-robbins/micropython,puuu/micropython,MrSurly/micropython-esp32,pramasoul/micropython,pozetroninc/micropython,alex-robbins/micropython,PappaPeppar/micropython,Timmenem/micropython,MrSurly/micropython-esp32,MrSurly/micropython