[kbuild] change architecture Makefiles not to overwrite

CFLAGS, instead append them to the existing CFLAGS.
	 Also, remove all double CFLAGS

arch/arm/Makefile

@@ -20,7 +20,7 @@ cpu-$(CONFIG_ARM926EJS)            := arm926ejs
 TEXT_BASE = $(CONFIG_TEXT_BASE)
 
 CPPFLAGS += -mabi=apcs-gnu -DTEXT_BASE=$(TEXT_BASE) -P
-CFLAGS := -fno-common -msoft-float -Os
+CFLAGS += -msoft-float -Os
 
 # Add cleanup flags
 CPPFLAGS += -fdata-sections -ffunction-sections

arch/blackfin/Makefile

@@ -9,7 +9,7 @@ cpu-$(CONFIG_BF561)		:= bf561
 TEXT_BASE = $(CONFIG_TEXT_BASE)
 
 CPPFLAGS += -DTEXT_BASE=$(TEXT_BASE) -P
-CFLAGS := -fno-common -Os -D__blackfin__
+CFLAGS += -Os -D__blackfin__
 # -Ttext $(TEXT_BASE)
 KALLSYMS         += --symbol-prefix=_
 

arch/m68k/Makefile

@@ -41,9 +41,8 @@ TEXT_BASE = $(CONFIG_TEXT_BASE)
 CPPFLAGS += -DTEXT_BASE=$(TEXT_BASE) -P
 AFLAGS += -gdwarf-2 -save-temps
 # FIXME - remove overide
-CFLAGS := -Wall -Wundef -Wstrict-prototypes \
-  -msoft-float -mcfv4e -gdwarf-2 -feliminate-unused-debug-types \
-  -fmerge-all-constants -Os
+CFLAGS += -msoft-float -mcfv4e -gdwarf-2 -feliminate-unused-debug-types \
+	-fmerge-all-constants -Os
 # Incompatible code in U-Boot for -std=c99
 LDFLAGS_uboot  :=-L $(shell dirname `$(CC) $(CFLAGS) -print-libgcc-file-name`) -lgcc
 #  --verbose --stats

arch/ppc/Makefile

@@ -15,7 +15,7 @@ cpu-$(CONFIG_ARCH_MPC5200)			:= mpc5xxx
 TEXT_BASE = $(CONFIG_TEXT_BASE)
 
 CPPFLAGS += -DTEXT_BASE=$(TEXT_BASE) -P
-CFLAGS := -fno-common -Os
+CFLAGS += -Os
 
 ifeq ($(incdir-y),)
 incdir-y := $(machine-y)

arch/sandbox/Makefile

@@ -11,7 +11,7 @@ lds-y   := arch/sandbox/lib/u-boot.lds
 TEXT_BASE = $(CONFIG_TEXT_BASE)
 
 CPPFLAGS += -P
-CFLAGS := -fno-common -Os -Dmalloc=u_boot_malloc \
+CFLAGS += -Os -Dmalloc=u_boot_malloc \
 		-Dfree=u_boot_free -Drealloc=u_boot_realloc \
 		-Dread=u_boot_read -Dwrite=u_boot_write \
 		-Dopen=u_boot_open -Dclose=u_boot_close \