[llvm] [llvm] Add format check for MCSubtargetFeatures (PR #180943)

[via llvm-commits]

github-actions[bot] wrote:

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

The build failed before running any tests. Click on a failure below to see the details.

<details>
<summary>[code=1] lib/MC/CMakeFiles/LLVMMC.dir/TargetRegistry.cpp.obj</summary>

```
FAILED: [code=1] lib/MC/CMakeFiles/LLVMMC.dir/TargetRegistry.cpp.obj
sccache C:\clang\clang-msvc\bin\clang-cl.exe  /nologo -TP -DUNICODE -D_CRT_NONSTDC_NO_DEPRECATE -D_CRT_NONSTDC_NO_WARNINGS -D_CRT_SECURE_NO_DEPRECATE -D_CRT_SECURE_NO_WARNINGS -D_GLIBCXX_ASSERTIONS -D_HAS_EXCEPTIONS=0 -D_SCL_SECURE_NO_DEPRECATE -D_SCL_SECURE_NO_WARNINGS -D_UNICODE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -Ilib\MC -IC:\_work\llvm-project\llvm-project\llvm\lib\MC -Iinclude -IC:\_work\llvm-project\llvm-project\llvm\include /DWIN32 /D_WINDOWS   /Zc:inline /Zc:__cplusplus /Oi /Brepro /bigobj /permissive- -Werror=unguarded-availability-new /W4  -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wmissing-field-initializers -Wimplicit-fallthrough -Wcovered-switch-default -Wno-noexcept-type -Wnon-virtual-dtor -Wdelete-non-virtual-dtor -Wsuggest-override -Wstring-conversion -Wno-pass-failed -Wmisleading-indentation -Wctad-maybe-unsupported /Gw /O2 /Ob2  -MD -UNDEBUG /EHs-c- /GR- -std:c++17 /showIncludes /Folib\MC\CMakeFiles\LLVMMC.dir\TargetRegistry.cpp.obj /Fdlib\MC\CMakeFiles\LLVMMC.dir\LLVMMC.pdb -c -- C:\_work\llvm-project\llvm-project\llvm\lib\MC\TargetRegistry.cpp
C:\_work\llvm-project\llvm-project\llvm\lib\MC\TargetRegistry.cpp(26,57): error: non-member function cannot have 'const' qualifier
26 | bool isValidFeatureListFormat(StringRef FeaturesString) const {
|                                                         ^~~~~
1 error generated.
```
</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/180943