FIX: Clang and MSVC compile options duplicate for clang-cl

[JKot-Coder]

Summary

When building with clang-cl (Clang frontend for MSVC):

• Previously, both Clang-specific and MSVC-specific compiler flags were applied, producing duplicate warnings and huge warning output.
• Compilation could slow down by orders of magnitude due to -Wall/-Wextra.

Changes

• Clang-cl now only uses MSVC-specific compile options.
• Pure Clang builds continue using Clang-specific warnings and suppressions.
• Redundant -Wall/-Wextra removed for clang-cl.

Benefits

• Builds with clang-cl are significantly faster.
• Warning output is reasonable and manageable.
• Maintains correct compile flags for each compiler.

[TheMostDiligent]

There are a few other places where clang-specific compiler options are set e.g. Should they also be disabled for clang-cl?

https://github.com/DiligentGraphics/DiligentCore/blob/c4a98bd5d210d5ed093aee0f4715ead530466acf/Graphics/ShaderTools/CMakeLists.txt#L141-L143

https://github.com/DiligentGraphics/DiligentCore/blob/c4a98bd5d210d5ed093aee0f4715ead530466acf/Graphics/ShaderTools/CMakeLists.txt#L146-L149

https://github.com/DiligentGraphics/DiligentCore/blob/c4a98bd5d210d5ed093aee0f4715ead530466acf/Graphics/GraphicsEngineOpenGL/CMakeLists.txt#L223-L248

https://github.com/DiligentGraphics/DiligentCore/blob/c4a98bd5d210d5ed093aee0f4715ead530466acf/Tests/DiligentCoreTest/CMakeLists.txt#L25-L32

https://github.com/DiligentGraphics/DiligentCore/blob/c4a98bd5d210d5ed093aee0f4715ead530466acf/Tests/GPUTestFramework/CMakeLists.txt#L126-L141

https://github.com/DiligentGraphics/DiligentCore/blob/c4a98bd5d210d5ed093aee0f4715ead530466acf/Tests/DiligentCoreAPITest/CMakeLists.txt#L128-L141

[JKot-Coder]

I'm 99% sure they all should be fixed same way. But I didn't checked any of this. I'm just started use Diligent and faced with issued that clang++ fails to link at windows. clang-cl - fails to compile 😄 So I'm just fixed most critical one issues for me. I'm use complied only core and dx12 for now.

[TheMostDiligent]

Did you figure out how to make the build faster? Last time I tried clang-cl, it took almost 1.5 hours to build everything.

[TheMostDiligent]

This change does not seem to be correct. If clang-cl only takes MSVC-like command line arguments, the entire branch should be disabled:

if (CMAKE_CXX_COMPILER_ID MATCHES "Clang" AND NOT MSVC)

This reduces the number of warnings, but build time is still ridiculous. It takes more than 5 minutes to build only Diligent-GraphicsEngineD3D11-static

[JKot-Coder]

if (CMAKE_CXX_COMPILER_ID MATCHES "Clang" AND NOT MSVC) Yes, that makes sense.

With all errors ignored using -w, the build completed in less than a minute. Warnings significantly affect build performance.

[TheMostDiligent]

For me, it feels like linking takes most of the time. Which generator do you use? VS or Ninja?