kbuild: enable 'make CFLAGS=...' to add additional options to CC

The variable CFLAGS is a wellknown variable and the usage by
kbuild may result in unexpected behaviour.
On top of that several people over time has asked for a way to
pass in additional flags to gcc.

This patch replace use of CFLAGS with KBUILD_CFLAGS all over the
tree and enabling one to use:
make CFLAGS=...
to specify additional gcc commandline options.

One usecase is when trying to find gcc bugs but other
use cases has been requested too.

Patch was tested on following architectures:
alpha, arm, i386, x86_64, mips, sparc, sparc64, ia64, m68k

Test was simple to do a defconfig build, apply the patch and check
that nothing got rebuild.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

1 files changed, 2 insertions, 2 deletions

diff --git a/arch/x86/vdso/Makefile b/arch/x86/vdso/Makefile
index 8d03de029d9b..dcd6bb9e0bb3 100644
--- a/arch/x86/vdso/Makefile
+++ b/arch/x86/vdso/Makefile
@@ -34,8 +34,8 @@ $(obj)/vdso.so: $(src)/vdso.lds $(vobjs) FORCE
 
 CFL := $(PROFILING) -mcmodel=small -fPIC -g0 -O2 -fasynchronous-unwind-tables -m64
 
-$(obj)/vclock_gettime.o: CFLAGS = $(CFL)
-$(obj)/vgetcpu.o: CFLAGS = $(CFL)
+$(obj)/vclock_gettime.o: KBUILD_CFLAGS = $(CFL)
+$(obj)/vgetcpu.o: KBUILD_CFLAGS = $(CFL)
 
 # We also create a special relocatable object that should mirror the symbol
 # table and layout of the linked DSO.  With ld -R we can then refer to