FAILED: patch "[PATCH] arm64: vdso32: Fix '--prefix=' value for newer versions of" failed to apply to 4.19-stable tree

The patch below does not apply to the 4.19-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 7b7891c7bdfd61fc9ed6747a0a05efe2394dddc6 Mon Sep 17 00:00:00 2001
From: Nathan Chancellor <[email protected]>
Date: Wed, 22 Jul 2020 21:15:10 -0700
Subject: [PATCH] arm64: vdso32: Fix '--prefix=' value for newer versions of
clang

Newer versions of clang only look for $(COMPAT_GCC_TOOLCHAIN_DIR)as [1], rather than $(COMPAT_GCC_TOOLCHAIN_DIR)$(CROSS_COMPILE_COMPAT)as, resulting in the following build error:

$ make -skj"$(nproc)" ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- \
CROSS_COMPILE_COMPAT=arm-linux-gnueabi- LLVM=1 O=out/aarch64 distclean \
defconfig arch/arm64/kernel/vdso32/
...
/home/nathan/cbl/toolchains/llvm-binutils/bin/as: unrecognized option '-EL'
clang-12: error: assembler command failed with exit code 1 (use -v to see invocation)
make[3]: *** [arch/arm64/kernel/vdso32/Makefile:181: arch/arm64/kernel/vdso32/note.o] Error 1
...

Adding the value of CROSS_COMPILE_COMPAT (adding notdir to account for a full path for CROSS_COMPILE_COMPAT) fixes this issue, which matches the solution done for the main Makefile [2].

[1]: https://github.com/llvm/llvm-project/commit/3452a0d8c17f7166f479706b293caf6ac76ffd90
[2]: https://lore.kernel.org/lkml/[email protected]/

index d88148bef6b0..5139a5f19256 100644
@@ -14,7 +14,7 @@ COMPAT_GCC_TOOLCHAIN_DIR := $(dir $(shell which $(CROSS_COMPILE_COMPAT)elfedit))
 COMPAT_GCC_TOOLCHAIN := $(realpath $(COMPAT_GCC_TOOLCHAIN_DIR)/..)
 
 CC_COMPAT_CLANG_FLAGS := --target=$(notdir $(CROSS_COMPILE_COMPAT:%-=%))
-CC_COMPAT_CLANG_FLAGS += --prefix=$(COMPAT_GCC_TOOLCHAIN_DIR)
+CC_COMPAT_CLANG_FLAGS += --prefix=$(COMPAT_GCC_TOOLCHAIN_DIR)$(notdir $(CROSS_COMPILE_COMPAT))
 CC_COMPAT_CLANG_FLAGS += -no-integrated-as -Qunused-arguments
 ifneq ($(COMPAT_GCC_TOOLCHAIN),)
 CC_COMPAT_CLANG_FLAGS += --gcc-toolchain=$(COMPAT_GCC_TOOLCHAIN)