make build on ARM easier (#34607)
make build on ARM easier (#34607)

* small improvements for build on ARM

* add missing space

* add note about SourceLink on ARM

shimingsg/corefx,ptoonen/corefx,ericstj/corefx,ViktorHofer/corefx,wtgodbe/corefx,shimingsg/corefx,shimingsg/corefx,ericstj/corefx,wtgodbe/corefx,shimingsg/corefx,wtgodbe/corefx,ViktorHofer/corefx,BrennanConroy/corefx,ViktorHofer/corefx,wtgodbe/corefx,ptoonen/corefx,shimingsg/corefx,ericstj/corefx,ericstj/corefx,BrennanConroy/corefx,ptoonen/corefx,shimingsg/corefx,wtgodbe/corefx,ericstj/corefx,wtgodbe/corefx,ptoonen/corefx,wtgodbe/corefx,shimingsg/corefx,ptoonen/corefx,ericstj/corefx,BrennanConroy/corefx,ViktorHofer/corefx,ptoonen/corefx,ViktorHofer/corefx,ViktorHofer/corefx,ptoonen/corefx,ericstj/corefx,ViktorHofer/corefx