All Makefiles now use MACHINE_ARCH for the target architecture.
Unification is required for cross-building.
Tags added to:
sys/boot/Makefile
sys/boot/arc/loader/Makefile
sys/kern/Makefile
usr.bin/cpp/Makefile
usr.bin/gcore/Makefile
usr.bin/truss/Makefile
usr.bin/gcore/Makefile:
fixed typo: MACHINDE -> MACHINE_ARCH