[llvm] [llvm] Use llvm::copy (NFC) (PR #137470)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `clang-aarch64-sve2-vla-2stage` running on `linaro-g4-02` while building `llvm` at step 12 "ninja check 2".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/199/builds/3015

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 12 (ninja check 2) failure: stage 2 checked (failure)
...
[679/1398] Linking CXX executable tools/clang/unittests/Format/FormatTests
clang++: warning: argument unused during compilation: '-mllvm -scalable-vectorization=preferred' [-Wunused-command-line-argument]
clang++: warning: argument unused during compilation: '-mllvm -treat-scalable-fixed-error-as-warning=false' [-Wunused-command-line-argument]
[683/1398] Linking CXX executable tools/clang/unittests/AST/ASTTests
clang++: warning: argument unused during compilation: '-mllvm -scalable-vectorization=preferred' [-Wunused-command-line-argument]
clang++: warning: argument unused during compilation: '-mllvm -treat-scalable-fixed-error-as-warning=false' [-Wunused-command-line-argument]
[780/1398] Linking CXX executable unittests/BinaryFormat/BinaryFormatTests
clang++: warning: argument unused during compilation: '-mllvm -scalable-vectorization=preferred' [-Wunused-command-line-argument]
clang++: warning: argument unused during compilation: '-mllvm -treat-scalable-fixed-error-as-warning=false' [-Wunused-command-line-argument]
[783/1398] Linking CXX executable unittests/AsmParser/AsmParserTests
FAILED: unittests/AsmParser/AsmParserTests 
: && /home/tcwg-buildbot/worker/clang-aarch64-sve2-vla-2stage/stage1.install/bin/clang++ -mcpu=neoverse-v2 -mllvm -scalable-vectorization=preferred -mllvm -treat-scalable-fixed-error-as-warning=false -fPIC -fno-semantic-interposition -fvisibility-inlines-hidden -Werror=date-time -Werror=unguarded-availability-new -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wmissing-field-initializers -pedantic -Wno-long-long -Wc++98-compat-extra-semi -Wimplicit-fallthrough -Wcovered-switch-default -Wno-noexcept-type -Wnon-virtual-dtor -Wdelete-non-virtual-dtor -Wsuggest-override -Wno-comment -Wstring-conversion -Wmisleading-indentation -Wctad-maybe-unsupported -fdiagnostics-color -ffunction-sections -fdata-sections -O3 -DNDEBUG -fuse-ld=lld -Wl,--color-diagnostics    -Wl,--gc-sections unittests/AsmParser/CMakeFiles/AsmParserTests.dir/AsmParserTest.cpp.o -o unittests/AsmParser/AsmParserTests  lib/libLLVMAsmParser.a  lib/libLLVMCore.a  lib/libLLVMSupport.a  lib/libLLVMSupport.a  lib/libllvm_gtest_main.a  lib/libllvm_gtest.a  lib/libLLVMRemarks.a  lib/libLLVMBitstreamReader.a  lib/libLLVMBinaryFormat.a  lib/libLLVMTargetParser.a  lib/libLLVMSupport.a  lib/libLLVMDemangle.a  -lrt  -ldl  -lm  /usr/lib/aarch64-linux-gnu/libz.so  -lpthread && :
clang++: error: no such file or directory: 'lib/libllvm_gtest.a'
[829/1398] Building CXX object unittests/CodeGen/CMakeFiles/CodeGenTests.dir/TestAsmPrinter.cpp.o
[831/1398] Building CXX object unittests/ADT/CMakeFiles/ADTTests.dir/SmallVectorTest.cpp.o
[832/1398] Building CXX object unittests/CodeGen/CMakeFiles/CodeGenTests.dir/InstrRefLDVTest.cpp.o
ninja: build stopped: subcommand failed.

```

</details>

https://github.com/llvm/llvm-project/pull/137470