Modified config to explicitly update cumulative attributes in targets
Modified config to explicitly update cumulative attributes in targets

Modified '_process_config_and_overrides' to update cumulative
attributes based on cumulative overrides found during walking config
files.

This should remove most of the disparity between the config target
cumulative overrides and cumulative attributes set in targets.json.
These cumulative overrides are updated after the global target
instantiation though, which may cause internal build tool state
dependent on cumulative attributes to not correctly reflect all
cumulative overrides.

c1728p9/mbed-os,ryankurte/mbed-os,adamgreen/mbed,svogl/mbed-os,svastm/mbed,CalSol/mbed,bcostm/mbed-os,HeadsUpDisplayInc/mbed,Archcady/mbed-os,RonEld/mbed,mikaleppanen/mbed-os,CalSol/mbed,nvlsianpu/mbed,rgrover/mbed,karsev/mbed-os,NXPmicro/mbed,adamgreen/mbed,screamerbg/mbed,tung7970/mbed-os,maximmbed/mbed,geky/mbed,catiedev/mbed-os,mmorenobarm/mbed-os,NXPmicro/mbed,mmorenobarm/mbed-os,monkiineko/mbed-os,infinnovation/mbed-os,fanghuaqi/mbed,theotherjimmy/mbed,svastm/mbed,pradeep-gr/mbed-os5-onsemi,fvincenzo/mbed-os,andcor02/mbed-os,tung7970/mbed-os-1,bcostm/mbed-os,mbedmicro/mbed,screamerbg/mbed,arostm/mbed-os,monkiineko/mbed-os,nvlsianpu/mbed,pradeep-gr/mbed-os5-onsemi,maximmbed/mbed,svastm/mbed,RonEld/mbed,adustm/mbed,rgrover/mbed,arostm/mbed-os,fahhem/mbed-os,svogl/mbed-os,fanghuaqi/mbed,mikaleppanen/mbed-os,svastm/mbed,bulislaw/mbed-os,andreaslarssonublox/mbed,radhika-raghavendran/mbed-os5.1-onsemi,infinnovation/mbed-os,mbedmicro/mbed,fanghuaqi/mbed,karsev/mbed-os,ryankurte/mbed-os,bulislaw/mbed-os,karsev/mbed-os,monkiineko/mbed-os,adamgreen/mbed,nvlsianpu/mbed,HeadsUpDisplayInc/mbed,mbedmicro/mbed,fanghuaqi/mbed,maximmbed/mbed,monkiineko/mbed-os,adamgreen/mbed,RonEld/mbed,catiedev/mbed-os,mazimkhan/mbed-os,arostm/mbed-os,radhika-raghavendran/mbed-os5.1-onsemi,jeremybrodt/mbed,c1728p9/mbed-os,j-greffe/mbed-os,geky/mbed,radhika-raghavendran/mbed-os5.1-onsemi,catiedev/mbed-os,mikaleppanen/mbed-os,fahhem/mbed-os,j-greffe/mbed-os,tung7970/mbed-os,mbedmicro/mbed,karsev/mbed-os,fvincenzo/mbed-os,rgrover/mbed,kjbracey-arm/mbed,adustm/mbed,RonEld/mbed,fvincenzo/mbed-os,NXPmicro/mbed,betzw/mbed-os,tung7970/mbed-os-1,nRFMesh/mbed-os,bcostm/mbed-os,betzw/mbed-os,mbedmicro/mbed,netzimme/mbed-os,fanghuaqi/mbed,ryankurte/mbed-os,kjbracey-arm/mbed,andcor02/mbed-os,maximmbed/mbed,RonEld/mbed,radhika-raghavendran/mbed-os5.1-onsemi,svogl/mbed-os,mazimkhan/mbed-os,YarivCol/mbed-os,adamgreen/mbed,kl-cruz/mbed-os,CalSol/mbed,jeremybrodt/mbed,andreaslarssonublox/mbed,j-greffe/mbed-os,tung7970/mbed-os,theotherjimmy/mbed,andcor02/mbed-os,betzw/mbed-os,j-greffe/mbed-os,netzimme/mbed-os,Archcady/mbed-os,jeremybrodt/mbed,YarivCol/mbed-os,fahhem/mbed-os,netzimme/mbed-os,screamerbg/mbed,arostm/mbed-os,betzw/mbed-os,rgrover/mbed,fahhem/mbed-os,j-greffe/mbed-os,nvlsianpu/mbed,maximmbed/mbed,svogl/mbed-os,netzimme/mbed-os,geky/mbed,Archcady/mbed-os,netzimme/mbed-os,tung7970/mbed-os,jeremybrodt/mbed,mikaleppanen/mbed-os,kjbracey-arm/mbed,HeadsUpDisplayInc/mbed,Archcady/mbed-os,bcostm/mbed-os,kl-cruz/mbed-os,rgrover/mbed,infinnovation/mbed-os,screamerbg/mbed,jeremybrodt/mbed,fahhem/mbed-os,nvlsianpu/mbed,fahhem/mbed-os,adamgreen/mbed,mikaleppanen/mbed-os,screamerbg/mbed,c1728p9/mbed-os,radhika-raghavendran/mbed-os5.1-onsemi,kl-cruz/mbed-os,geky/mbed,mmorenobarm/mbed-os,svastm/mbed,catiedev/mbed-os,ryankurte/mbed-os,pradeep-gr/mbed-os5-onsemi,nRFMesh/mbed-os,adustm/mbed,Archcady/mbed-os,j-greffe/mbed-os,monkiineko/mbed-os,bulislaw/mbed-os,theotherjimmy/mbed,adustm/mbed,CalSol/mbed,ryankurte/mbed-os,YarivCol/mbed-os,cvtsi2sd/mbed-os,c1728p9/mbed-os,betzw/mbed-os,andreaslarssonublox/mbed,mmorenobarm/mbed-os,kl-cruz/mbed-os,adustm/mbed,kl-cruz/mbed-os,bulislaw/mbed-os,screamerbg/mbed,pradeep-gr/mbed-os5-onsemi,andcor02/mbed-os,YarivCol/mbed-os,bulislaw/mbed-os,bcostm/mbed-os,theotherjimmy/mbed,bcostm/mbed-os,nRFMesh/mbed-os,mikaleppanen/mbed-os,NXPmicro/mbed,mmorenobarm/mbed-os,cvtsi2sd/mbed-os,cvtsi2sd/mbed-os,ryankurte/mbed-os,mazimkhan/mbed-os,radhika-raghavendran/mbed-os5.1-onsemi,catiedev/mbed-os,tung7970/mbed-os-1,infinnovation/mbed-os,c1728p9/mbed-os,fvincenzo/mbed-os,YarivCol/mbed-os,nRFMesh/mbed-os,maximmbed/mbed,c1728p9/mbed-os,betzw/mbed-os,infinnovation/mbed-os,infinnovation/mbed-os,fvincenzo/mbed-os,monkiineko/mbed-os,tung7970/mbed-os,kl-cruz/mbed-os,catiedev/mbed-os,cvtsi2sd/mbed-os,arostm/mbed-os,andcor02/mbed-os,CalSol/mbed,HeadsUpDisplayInc/mbed,andcor02/mbed-os,svogl/mbed-os,adustm/mbed,nRFMesh/mbed-os,geky/mbed,mazimkhan/mbed-os,nvlsianpu/mbed,Archcady/mbed-os,theotherjimmy/mbed,pradeep-gr/mbed-os5-onsemi,arostm/mbed-os,NXPmicro/mbed,cvtsi2sd/mbed-os,tung7970/mbed-os-1,theotherjimmy/mbed,pradeep-gr/mbed-os5-onsemi,kjbracey-arm/mbed,RonEld/mbed,karsev/mbed-os,andreaslarssonublox/mbed,svogl/mbed-os,netzimme/mbed-os,NXPmicro/mbed,andreaslarssonublox/mbed,bulislaw/mbed-os,mmorenobarm/mbed-os,YarivCol/mbed-os,HeadsUpDisplayInc/mbed,mazimkhan/mbed-os,CalSol/mbed,tung7970/mbed-os-1,nRFMesh/mbed-os,cvtsi2sd/mbed-os,karsev/mbed-os,HeadsUpDisplayInc/mbed,mazimkhan/mbed-os