This adds the reverse of CFLAGS_obj.o with CFLAGS_REMOVE_obj.o.
This allows to prevent certain CFLAGS from being used to
compile files.

travis-ci: success for series starting with [1/6] compel/infect: fix out-of-bounds parasite memcpy()
Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Dmitry Safonov <dsafonov@virtuozzo.com>
Reviewed-by: Dmitry Safonov <dsafonov@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>