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>

2 files changed, 4 insertions, 6 deletions

diff --git a/arch/xtensa/Makefile b/arch/xtensa/Makefile
index acf05be24929..56685a883347 100644
--- a/arch/xtensa/Makefile
+++ b/arch/xtensa/Makefile
@@ -28,11 +28,9 @@ PLATFORM = $(platform-y)
 export PLATFORM
 
 # temporarily until string.h is fixed
-cflags-y += -ffreestanding
+KBUILD_CFLAGS += -ffreestanding
 
-cflags-y += -pipe -mlongcalls
-
-CFLAGS  += $(cflags-y)
+KBUILD_CFLAGS += -pipe -mlongcalls
 
 KBUILD_DEFCONFIG := iss_defconfig
 
@@ -56,7 +54,7 @@ endif
 
 #
 
-LIBGCC := $(shell $(CC) $(CFLAGS) -print-libgcc-file-name)
+LIBGCC := $(shell $(CC) $(KBUILD_CFLAGS) -print-libgcc-file-name)
 
 head-y          := arch/xtensa/kernel/head.o
 core-y          += arch/xtensa/kernel/ arch/xtensa/mm/
diff --git a/arch/xtensa/boot/boot-redboot/Makefile b/arch/xtensa/boot/boot-redboot/Makefile
index f53262c2e1f3..74d15d08077b 100644
--- a/arch/xtensa/boot/boot-redboot/Makefile
+++ b/arch/xtensa/boot/boot-redboot/Makefile
@@ -19,7 +19,7 @@ boot-y	:= bootstrap.o
 OBJS    := $(addprefix $(obj)/,$(boot-y))
 LIBS    := arch/xtensa/boot/lib/lib.a arch/xtensa/lib/lib.a
 
-LIBGCC := $(shell $(CC) $(CFLAGS) -print-libgcc-file-name)
+LIBGCC := $(shell $(CC) $(KBUILD_CFLAGS) -print-libgcc-file-name)
 
 zImage: vmlinux $(OBJS) $(LIBS)
         $(OBJCOPY) --strip-all -R .comment -R .xt.insn -O binary \