Recent changed to the j2se makefiles allowed for per-file optimization settings with things like:

CFLAGS_OPT/foobar.o = -xO1

which would change the value of CFLAGS_OPT. But the CFLAGS_OPT variable contained other settings like -Xa, so a slight change in the makefiles was needed to make sure only opt settings were in these variables.

See suggested fix.