[clang] [Clang] Add warning for non-portable include paths with trailing whitespace or dots (PR #190610)

[via cfe-commits]

github-actions[bot] wrote:

<!--PREMERGE ADVISOR COMMENT: Windows-->
# :window: Windows x64 Test Results

* 53500 tests passed
* 1068 tests skipped
* 1 test failed

## Failed Tests
(click on a test name to see its output)

### Clang
<details>
<summary>Clang.Preprocessor/nonportable-trailing-whitespace.c</summary>

```
Exit Code: 1

Command Output (stdout):
--
# RUN: at line 1
rm -rf C:\_work\llvm-project\llvm-project\build\tools\clang\test\Preprocessor\Output\nonportable-trailing-whitespace.c.tmp
# executed command: rm -rf 'C:\_work\llvm-project\llvm-project\build\tools\clang\test\Preprocessor\Output\nonportable-trailing-whitespace.c.tmp'
# note: command had no output on stdout or stderr
# RUN: at line 2
mkdir -p C:\_work\llvm-project\llvm-project\build\tools\clang\test\Preprocessor\Output\nonportable-trailing-whitespace.c.tmp
# executed command: mkdir -p 'C:\_work\llvm-project\llvm-project\build\tools\clang\test\Preprocessor\Output\nonportable-trailing-whitespace.c.tmp'
# note: command had no output on stdout or stderr
# RUN: at line 3
touch C:\_work\llvm-project\llvm-project\build\tools\clang\test\Preprocessor\Output\nonportable-trailing-whitespace.c.tmp/simple.h
# executed command: touch 'C:\_work\llvm-project\llvm-project\build\tools\clang\test\Preprocessor\Output\nonportable-trailing-whitespace.c.tmp/simple.h'
# note: command had no output on stdout or stderr
# RUN: at line 4
c:\_work\llvm-project\llvm-project\build\bin\clang.exe -cc1 -internal-isystem C:\_work\llvm-project\llvm-project\build\lib\clang\23\include -nostdsysteminc -fsyntax-only -IC:\_work\llvm-project\llvm-project\build\tools\clang\test\Preprocessor\Output\nonportable-trailing-whitespace.c.tmp -Wnonportable-include-path -verify C:\_work\llvm-project\llvm-project\clang\test\Preprocessor\nonportable-trailing-whitespace.c
# executed command: 'c:\_work\llvm-project\llvm-project\build\bin\clang.exe' -cc1 -internal-isystem 'C:\_work\llvm-project\llvm-project\build\lib\clang\23\include' -nostdsysteminc -fsyntax-only '-IC:\_work\llvm-project\llvm-project\build\tools\clang\test\Preprocessor\Output\nonportable-trailing-whitespace.c.tmp' -Wnonportable-include-path -verify 'C:\_work\llvm-project\llvm-project\clang\test\Preprocessor\nonportable-trailing-whitespace.c'
# .---command stderr------------
# | error: 'expected-error' diagnostics expected but not seen: 
# |   File C:\_work\llvm-project\llvm-project\clang\test\Preprocessor\nonportable-trailing-whitespace.c Line 7: 'simple.h ' file not found
# |   File C:\_work\llvm-project\llvm-project\clang\test\Preprocessor\nonportable-trailing-whitespace.c Line 11: 'simple.h.' file not found
# | 2 errors generated.
# `-----------------------------
# error: command failed with exit status: 1

--

```
</details>

If these failures are unrelated to your changes (for example tests are broken or flaky at HEAD), please open an issue at https://github.com/llvm/llvm-project/issues and add the `infrastructure` label.

https://github.com/llvm/llvm-project/pull/190610