MIPS: VDSO: Use CLANG_FLAGS instead of filtering out '--target='

commit 76d7fff2 upstream.

Commit ee67855e ("MIPS: vdso: Allow clang's --target flag in VDSO
cflags") allowed the '--target=' flag from the main Makefile to filter
through to the vDSO. However, it did not bring any of the other clang
specific flags for controlling the integrated assembler and the GNU
tools locations (--prefix=, --gcc-toolchain=, and -no-integrated-as).
Without these, we will get a warning (visible with tinyconfig):

arch/mips/vdso/elf.S:14:1: warning: DWARF2 only supports one section per
compilation unit
.pushsection .note.Linux, "a",@note ; .balign 4 ; .long 2f - 1f ; .long
4484f - 3f ; .long 0 ; 1:.asciz "Linux" ; 2:.balign 4 ; 3:
^
arch/mips/vdso/elf.S:34:2: warning: DWARF2 only supports one section per
compilation unit
 .section .mips_abiflags, "a"
 ^

All of these flags are bundled up under CLANG_FLAGS in the main Makefile
and exported so that they can be added to Makefiles that set their own
CFLAGS. Use this value instead of filtering out '--target=' so there is
no warning and all of the tools are properly used.

Cc: stable@vger.kernel.org
Fixes: ee67855e ("MIPS: vdso: Allow clang's --target flag in VDSO cflags")
Link: https://github.com/ClangBuiltLinux/linux/issues/1256Reported-by: NAnders Roxell <anders.roxell@linaro.org>
Signed-off-by: NNathan Chancellor <natechancellor@gmail.com>
Tested-by: NAnders Roxell <anders.roxell@linaro.org>
Signed-off-by: NThomas Bogendoerfer <tsbogend@alpha.franken.de>
[nc: Fix conflict due to lack of 99570c3d and 076f421d in 4.19]
Signed-off-by: NNathan Chancellor <nathan@kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

arch/mips/vdso/Makefile

@@ -10,12 +10,9 @@ ccflags-vdso := \
 	$(filter -march=%,$(KBUILD_CFLAGS)) \
 	$(filter -m%-float,$(KBUILD_CFLAGS)) \
 	$(filter -mno-loongson-%,$(KBUILD_CFLAGS)) \
+	$(CLANG_FLAGS) \
 	-D__VDSO__
 
-ifeq ($(cc-name),clang)
-ccflags-vdso += $(filter --target=%,$(KBUILD_CFLAGS))
-endif
-
 cflags-vdso := $(ccflags-vdso) \
 	$(filter -W%,$(filter-out -Wa$(comma)%,$(KBUILD_CFLAGS))) \
 	-O2 -g -fPIC -fno-strict-aliasing -fno-common -fno-builtin -G 0 \