Makefile: move more flags to the top Makefile

Before this commit, most of compiler flags were defined in config.mk.
But it is redundant because config.mk is included from all recursive make.

This commit moves many complier flags to the top Makefile
and export them.
And we use new vaiarables to store them:
KBUILD_CPPFLAGS, KBUILD_CFLAGS, KBUILD_AFLAGS.
This will allow us to switch more smoothly to Kbuild.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>

config.mk

@@ -90,19 +90,13 @@ endif
 
 #########################################################################
 
-# We don't actually use $(ARFLAGS) anywhere anymore, so catch people
-# who are porting old code to latest mainline but not updating $(AR).
-ARFLAGS = $(error update your Makefile to use cmd_link_o_target and not AR)
 RELFLAGS= $(PLATFORM_RELFLAGS)
-DBGFLAGS= -g # -DDEBUG
-OPTFLAGS= -Os #-fomit-frame-pointer
 
 OBJCFLAGS += --gap-fill=0xff
 
 gccincdir := $(shell $(CC) -print-file-name=include)
 
-CPPFLAGS := $(DBGFLAGS) $(OPTFLAGS) $(RELFLAGS)		\
-	-D__KERNEL__
+CPPFLAGS = $(KBUILD_CPPFLAGS) $(RELFLAGS)
 
 # Enable garbage collection of un-used sections for SPL
 ifeq ($(CONFIG_SPL_BUILD),y)
@@ -134,26 +128,10 @@ CPPFLAGS += -I$(OBJTREE)/include
 endif
 
 CPPFLAGS += -I$(TOPDIR)/include -I$(SRCTREE)/arch/$(ARCH)/include
-CPPFLAGS += -fno-builtin -ffreestanding -nostdinc	\
+CPPFLAGS += -nostdinc	\
 	-isystem $(gccincdir) -pipe $(PLATFORM_CPPFLAGS)
 
-CFLAGS := $(CPPFLAGS) -Wall -Wstrict-prototypes
-
-ifdef BUILD_TAG
-CFLAGS += -DBUILD_TAG='"$(BUILD_TAG)"'
-endif
-
-CFLAGS_SSP := $(call cc-option,-fno-stack-protector)
-CFLAGS += $(CFLAGS_SSP)
-# Some toolchains enable security related warning flags by default,
-# but they don't make much sense in the u-boot world, so disable them.
-CFLAGS_WARN := $(call cc-option,-Wno-format-nonliteral) \
-	       $(call cc-option,-Wno-format-security)
-CFLAGS += $(CFLAGS_WARN)
-
-# Report stack usage if supported
-CFLAGS_STACK := $(call cc-option,-fstack-usage)
-CFLAGS += $(CFLAGS_STACK)
+CFLAGS := $(KBUILD_CFLAGS) $(CPPFLAGS)
 
 BCURDIR = $(subst $(SRCTREE)/,,$(CURDIR:$(obj)%=%))
 
@@ -165,18 +143,7 @@ endif
 endif
 endif
 
-# $(CPPFLAGS) sets -g, which causes gcc to pass a suitable -g<format>
-# option to the assembler.
-AFLAGS_DEBUG :=
-
-# turn jbsr into jsr for m68k
-ifeq ($(ARCH),m68k)
-ifeq ($(findstring 3.4,$(shell $(CC) --version)),3.4)
-AFLAGS_DEBUG := -Wa,-gstabs,-S
-endif
-endif
-
-AFLAGS := $(AFLAGS_DEBUG) -D__ASSEMBLY__ $(CPPFLAGS)
+AFLAGS := $(KBUILD_AFLAGS) $(CPPFLAGS)
 
 LDFLAGS += $(PLATFORM_LDFLAGS)
 LDFLAGS_FINAL += -Bstatic