arch: use cross_compiling to check whether it is a cross build or not

'cross_compiling' is defined by the top Makefile and available for
arch Makefiles to check whether it is a cross build or not. A good
thing is the variable name 'cross_compiling' is self-documenting.

This is a simple replacement for m68k, mips, sh, for which $(ARCH)
and $(SRCARCH) always match.

No functional change is intended for xtensa, either.

This is rather a fix for parisc because arch/parisc/Makefile defines
UTS_MATCHINE depending on CONFIG_64BIT, therefore cc-cross-prefix
is not working in Kconfig time.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Helge Deller <deller@gmx.de>  # parisc
Acked-by: Max Filippov <jcmvbkbc@gmail.com> # xtensa

arch/m68k/Makefile

@@ -16,7 +16,7 @@
 
 KBUILD_DEFCONFIG := multi_defconfig
 
-ifneq ($(SUBARCH),$(ARCH))
+ifdef cross_compiling
 	ifeq ($(CROSS_COMPILE),)
 		CROSS_COMPILE := $(call cc-cross-prefix, \
 			m68k-linux-gnu- m68k-linux- m68k-unknown-linux-gnu-)

arch/mips/Makefile

@@ -50,7 +50,7 @@ tool-archpref		= $(64bit-tool-archpref)
 UTS_MACHINE		:= mips64
 endif
 
-ifneq ($(SUBARCH),$(ARCH))
+ifdef cross_compiling
   ifeq ($(CROSS_COMPILE),)
     CROSS_COMPILE := $(call cc-cross-prefix, $(tool-archpref)-linux-  $(tool-archpref)-linux-gnu-  $(tool-archpref)-unknown-linux-gnu-)
   endif

arch/parisc/Makefile

@@ -41,7 +41,7 @@ endif
 
 export LD_BFD
 
-ifneq ($(SUBARCH),$(UTS_MACHINE))
+ifdef cross_compiling
 	ifeq ($(CROSS_COMPILE),)
 		CC_SUFFIXES = linux linux-gnu unknown-linux-gnu
 		CROSS_COMPILE := $(call cc-cross-prefix, \

arch/sh/Makefile

@@ -9,7 +9,7 @@
 # License.  See the file "COPYING" in the main directory of this archive
 # for more details.
 #
-ifneq ($(SUBARCH),$(ARCH))
+ifdef cross_compiling
   ifeq ($(CROSS_COMPILE),)
     CROSS_COMPILE := $(call cc-cross-prefix, sh-linux- sh-linux-gnu- sh-unknown-linux-gnu-)
   endif

arch/xtensa/Makefile

@@ -19,12 +19,8 @@ variant-y := $(patsubst "%",%,$(CONFIG_XTENSA_VARIANT_NAME))
 VARIANT = $(variant-y)
 export VARIANT
 
-# Test for cross compiling
-
 ifneq ($(VARIANT),)
-  COMPILE_ARCH = $(shell uname -m)
-
-  ifneq ($(COMPILE_ARCH), xtensa)
+  ifdef cross_compiling
     ifndef CROSS_COMPILE
       CROSS_COMPILE = xtensa_$(VARIANT)-
     endif