[clang] Clarify some code based on static analysis complaints; NFC (PR #145679)

[Aaron Ballman via cfe-commits]

AaronBallman wrote:

Windows precommit CI failures appear to be unrelated:
```
[6099/6110] Running clang_tools regression tests
llvm-lit.py: C:\_work\llvm-project\llvm-project\llvm\utils\lit\lit\llvm\config.py:57: note: using lit tools: C:\Program Files\Git\usr\bin
llvm-lit.py: C:\_work\llvm-project\llvm-project\llvm\utils\lit\lit\llvm\config.py:520: note: using clang: c:\_work\llvm-project\llvm-project\build\bin\clang.exe
llvm-lit.py: C:\_work\llvm-project\llvm-project\llvm\utils\lit\lit\llvm\config.py:312: fatal: Couldn't find the include dir for Clang ('c:\_work\llvm-project\llvm-project\build\bin\clang.exe')
c:\_work\llvm-project\llvm-project\build\bin\clang.exe
[6101/6110] Linking CXX executable bin\obj2yaml.exe
FAILED: tools/clang/tools/extra/CMakeFiles/check-clang-tools 
cmd.exe /C "cd /D C:\_work\llvm-project\llvm-project\build\tools\clang\tools\extra && C:\Python39\python.exe C:/_work/llvm-project/llvm-project/build/./bin/llvm-lit.py -v --xunit-xml-output C:/_work/llvm-project/llvm-project/build/test-results.xml --use-unique-output-file-name --timeout=1200 --time-tests C:/_work/llvm-project/llvm-project/build/tools/clang/tools/extra/include-cleaner/test C:/_work/llvm-project/llvm-project/build/tools/clang/tools/extra/clangd/test/../unittests C:/_work/llvm-project/llvm-project/build/tools/clang/tools/extra/clangd/test C:/_work/llvm-project/llvm-project/build/tools/clang/tools/extra/test"
[6103/6110] Linking CXX executable bin\clang.exe
```

https://github.com/llvm/llvm-project/pull/145679