kbuild: allow assignment to {A,C}FLAGS_KERNEL on the command line

It is now possible to assign options to AS and CC
on the command line - which is only used for built-in code.

{A,C}FLAGS_KERNEL was used both in the top-level Makefile
in the arch makefiles, thus users had no way to specify
additional options to AS, CC without overriding
the original value.

Introduce a new set of variables KBUILD_{A,C}FLAGS_KERNEL
that is used by arch specific files and free up
{A,C}FLAGS_KERNEL so they can be assigned on
the command line.

All arch Makefiles that used the old variables has been updated.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Hirokazu Takata <takata@linux-m32r.org>
Signed-off-by: Michal Marek <mmarek@suse.cz>
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 5e7c40e..a1a5cf9 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -118,7 +118,7 @@
 modkern_cflags =                                          \
 	$(if $(part-of-module),                           \
 		$(KBUILD_CFLAGS_MODULE) $(CFLAGS_MODULE), \
-		$(CFLAGS_KERNEL))
+		$(KBUILD_CFLAGS_KERNEL) $(CFLAGS_KERNEL))
 quiet_modtag := $(empty)   $(empty)
 
 $(real-objs-m)        : part-of-module := y
@@ -251,7 +251,7 @@
 # Compile assembler sources (.S)
 # ---------------------------------------------------------------------------
 
-modkern_aflags := $(AFLAGS_KERNEL)
+modkern_aflags := $(KBUILD_AFLAGS_KERNEL) $(AFLAGS_KERNEL)
 
 $(real-objs-m)      : modkern_aflags := $(KBUILD_AFLAGS_MODULE) $(AFLAGS_MODULE)
 $(real-objs-m:.o=.s): modkern_aflags := $(KBUILD_AFLAGS_MODULE) $(AFLAGS_MODULE)