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, 1 insertions, 1 deletions

diff --git a/arch/um/Makefile-x86_64 b/arch/um/Makefile-x86_64
index 69ecea63fdae..36d2bb5e4192 100644
--- a/arch/um/Makefile-x86_64
+++ b/arch/um/Makefile-x86_64
@@ -9,7 +9,7 @@ _extra_flags_ = -fno-builtin -m64
 #We #undef __x86_64__ for kernelspace, not for userspace where
 #it's needed for headers to work!
 ARCH_KERNEL_DEFINES = -U__$(SUBARCH)__
-CFLAGS += $(_extra_flags_)
+KBUILD_CFLAGS += $(_extra_flags_)
 
 CHECKFLAGS  += -m64
 AFLAGS += -m64