[clang-tools-extra] [include-cleaner] add fragment header support (PR #189458)

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github-actions[bot] wrote:

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

* 3137 tests passed
* 30 tests skipped
* 1 test failed

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

### ClangIncludeCleaner
<details>
<summary>ClangIncludeCleaner.ClangIncludeCleaner/fragments.cpp</summary>

```
Exit Code: 1

Command Output (stdout):
--
# RUN: at line 6
clang-include-cleaner -print=changes C:\_work\llvm-project\llvm-project\clang-tools-extra\include-cleaner\test\fragments.cpp --fragment-headers=.*\\.inc$ --fragment-dependency-comment-format='needed by {0}' -- -IC:\_work\llvm-project\llvm-project\clang-tools-extra\include-cleaner\test/Inputs/ | c:\_work\llvm-project\llvm-project\build\bin\filecheck.exe --check-prefix=CHANGES C:\_work\llvm-project\llvm-project\clang-tools-extra\include-cleaner\test\fragments.cpp
# executed command: clang-include-cleaner -print=changes 'C:\_work\llvm-project\llvm-project\clang-tools-extra\include-cleaner\test\fragments.cpp' '--fragment-headers=.*\\.inc$' '--fragment-dependency-comment-format=needed by {0}' -- '-IC:\_work\llvm-project\llvm-project\clang-tools-extra\include-cleaner\test/Inputs/'
# note: command had no output on stdout or stderr
# executed command: 'c:\_work\llvm-project\llvm-project\build\bin\filecheck.exe' --check-prefix=CHANGES 'C:\_work\llvm-project\llvm-project\clang-tools-extra\include-cleaner\test\fragments.cpp'
# .---command stderr------------
# | C:\_work\llvm-project\llvm-project\clang-tools-extra\include-cleaner\test\fragments.cpp:7:13: error: CHANGES: expected string not found in input
# | // CHANGES: ~ <vector> @Line:1 // needed by "gen.inc"
# |             ^
# | <stdin>:1:1: note: scanning from here
# | - <vector> @Line:1
# | ^
# | 
# | Input file: <stdin>
# | Check file: C:\_work\llvm-project\llvm-project\clang-tools-extra\include-cleaner\test\fragments.cpp
# | 
# | -dump-input=help explains the following input dump.
# | 
# | Input was:
# | <<<<<<
# |          1: - <vector> @Line:1 
# | check:7     X~~~~~~~~~~~~~~~~~~ error: no match found
# | >>>>>>
# `-----------------------------
# 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/189458