LoongArch: vDSO: Use CLANG_FLAGS instead of filtering out '--target='

This is a port of commit 76d7fff ("MIPS: VDSO: Use CLANG_FLAGS
instead of filtering out '--target='") to arch/loongarch, for fixing
cross-compilation with Clang.

Reported-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Link: ClangBuiltLinux#1787 (comment)
Signed-off-by: WANG Xuerui <git@xen0n.name>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

Author: xen0n

arch/loongarch/vdso/Makefile

@@ -12,12 +12,9 @@ ccflags-vdso := \
 	$(filter -E%,$(KBUILD_CFLAGS)) \
 	$(filter -march=%,$(KBUILD_CFLAGS)) \
 	$(filter -m%-float,$(KBUILD_CFLAGS)) \
+	$(CLANG_FLAGS) \
 	-D__VDSO__
 
-ifeq ($(cc-name),clang)
-ccflags-vdso += $(filter --target=%,$(KBUILD_CFLAGS))
-endif
-
 cflags-vdso := $(ccflags-vdso) \
 	-isystem $(shell $(CC) -print-file-name=include) \
 	$(filter -W%,$(filter-out -Wa$(comma)%,$(KBUILD_CFLAGS))) \