Commit 9a39e273d4 removed the boot directory
addition to CFLAGS that was being used by the subdirectory builds. For the
other files, that patch set EXTRA_CFLAGS, but Makefile.build explicitly
sets that to empty as it is explicitly for a single directory only.
Append to KBUILD_CFLAGS instead.
Signed-off-by: Milton Miller <[email protected]>
Signed-off-by: Sam Ravnborg <[email protected]>