kbuild: clang: do not use CROSS_COMPILE for target triple

The target triple is overridden by the user-supplied CROSS_COMPILE,
but I do not see a good reason to support it. Users can use a new
architecture without adding CLANG_TARGET_FLAGS_*, but that would be
a rare case.

Use the hard-coded and deterministic target triple all the time.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>

scripts/Makefile.clang

@@ -13,15 +13,11 @@ CLANG_TARGET_FLAGS_x86		:= x86_64-linux-gnu
 CLANG_TARGET_FLAGS_um		:= $(CLANG_TARGET_FLAGS_$(SUBARCH))
 CLANG_TARGET_FLAGS		:= $(CLANG_TARGET_FLAGS_$(SRCARCH))
 
-ifeq ($(CROSS_COMPILE),)
 ifeq ($(CLANG_TARGET_FLAGS),)
-$(error Specify CROSS_COMPILE or add '--target=' option to scripts/Makefile.clang)
+$(error add '--target=' option to scripts/Makefile.clang)
 else
 CLANG_FLAGS	+= --target=$(CLANG_TARGET_FLAGS)
-endif # CLANG_TARGET_FLAGS
-else
-CLANG_FLAGS	+= --target=$(notdir $(CROSS_COMPILE:%-=%))
-endif # CROSS_COMPILE
+endif
 
 ifeq ($(LLVM_IAS),0)
 CLANG_FLAGS	+= -fno-integrated-as