add COPTS and BUILD_COPTS to specify optimization flags without touching CFLAGS

Overriding CFLAGS and BUILD_CFLAGS from outside the build isn't really fun as
one then has to provide what comes in DEFINES and IPATH also. Add another flag
to set only the optimization flags and then combine it as before.

Signed-off-by: Rolf Eike Beer <eb@emlix.com>
Signed-off-by: Andrew G. Morgan <morgan@kernel.org>
1 file changed