[clang] [clang] Avoid creating temporary instances of std::string (NFC) (PR #140988)

[LLVM Continuous Integration via cfe-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `llvm-x86_64-debian-dylib` running on `gribozavr4` while building `clang` at step 8 "test-build-unified-tree-check-lld".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/60/builds/28113

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

```
Step 8 (test-build-unified-tree-check-lld) failure: test (failure)
******************** TEST 'lld :: COFF/lto-cache-errors.ll' FAILED ********************
Exit Code: 1

Command Output (stderr):
--
/b/1/llvm-x86_64-debian-dylib/build/bin/opt -module-hash -module-summary /b/1/llvm-x86_64-debian-dylib/llvm-project/lld/test/COFF/lto-cache-errors.ll -o /b/1/llvm-x86_64-debian-dylib/build/tools/lld/test/COFF/Output/lto-cache-errors.ll.tmp.o # RUN: at line 5
+ /b/1/llvm-x86_64-debian-dylib/build/bin/opt -module-hash -module-summary /b/1/llvm-x86_64-debian-dylib/llvm-project/lld/test/COFF/lto-cache-errors.ll -o /b/1/llvm-x86_64-debian-dylib/build/tools/lld/test/COFF/Output/lto-cache-errors.ll.tmp.o
/b/1/llvm-x86_64-debian-dylib/build/bin/opt -module-hash -module-summary /b/1/llvm-x86_64-debian-dylib/llvm-project/lld/test/COFF/Inputs/lto-cache.ll -o /b/1/llvm-x86_64-debian-dylib/build/tools/lld/test/COFF/Output/lto-cache-errors.ll.tmp2.o # RUN: at line 6
+ /b/1/llvm-x86_64-debian-dylib/build/bin/opt -module-hash -module-summary /b/1/llvm-x86_64-debian-dylib/llvm-project/lld/test/COFF/Inputs/lto-cache.ll -o /b/1/llvm-x86_64-debian-dylib/build/tools/lld/test/COFF/Output/lto-cache-errors.ll.tmp2.o
rm -Rf /b/1/llvm-x86_64-debian-dylib/build/tools/lld/test/COFF/Output/lto-cache-errors.ll.tmp.cache && mkdir /b/1/llvm-x86_64-debian-dylib/build/tools/lld/test/COFF/Output/lto-cache-errors.ll.tmp.cache # RUN: at line 7
+ rm -Rf /b/1/llvm-x86_64-debian-dylib/build/tools/lld/test/COFF/Output/lto-cache-errors.ll.tmp.cache
+ mkdir /b/1/llvm-x86_64-debian-dylib/build/tools/lld/test/COFF/Output/lto-cache-errors.ll.tmp.cache
chmod 444 /b/1/llvm-x86_64-debian-dylib/build/tools/lld/test/COFF/Output/lto-cache-errors.ll.tmp.cache # RUN: at line 8
+ chmod 444 /b/1/llvm-x86_64-debian-dylib/build/tools/lld/test/COFF/Output/lto-cache-errors.ll.tmp.cache
not /b/1/llvm-x86_64-debian-dylib/build/bin/lld-link /lldltocache:/b/1/llvm-x86_64-debian-dylib/build/tools/lld/test/COFF/Output/lto-cache-errors.ll.tmp.cache/nonexistant/ /out:/b/1/llvm-x86_64-debian-dylib/build/tools/lld/test/COFF/Output/lto-cache-errors.ll.tmp3 /entry:main /b/1/llvm-x86_64-debian-dylib/build/tools/lld/test/COFF/Output/lto-cache-errors.ll.tmp2.o /b/1/llvm-x86_64-debian-dylib/build/tools/lld/test/COFF/Output/lto-cache-errors.ll.tmp.o 2>&1 | /b/1/llvm-x86_64-debian-dylib/build/bin/FileCheck /b/1/llvm-x86_64-debian-dylib/llvm-project/lld/test/COFF/lto-cache-errors.ll # RUN: at line 11
+ /b/1/llvm-x86_64-debian-dylib/build/bin/FileCheck /b/1/llvm-x86_64-debian-dylib/llvm-project/lld/test/COFF/lto-cache-errors.ll
+ not /b/1/llvm-x86_64-debian-dylib/build/bin/lld-link /lldltocache:/b/1/llvm-x86_64-debian-dylib/build/tools/lld/test/COFF/Output/lto-cache-errors.ll.tmp.cache/nonexistant/ /out:/b/1/llvm-x86_64-debian-dylib/build/tools/lld/test/COFF/Output/lto-cache-errors.ll.tmp3 /entry:main /b/1/llvm-x86_64-debian-dylib/build/tools/lld/test/COFF/Output/lto-cache-errors.ll.tmp2.o /b/1/llvm-x86_64-debian-dylib/build/tools/lld/test/COFF/Output/lto-cache-errors.ll.tmp.o

--

********************


```

</details>

https://github.com/llvm/llvm-project/pull/140988