disable -Ofast for Clang >= 19

[zhuzeitou]

The -Ofast flag is deprecated in Clang 19 and later, causing frequent warnings during the build.
Exclude -Ofast for Clang versions >= 19 to suppress these warnings.

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[Copilot]

Pull request overview

Suppress Clang 19+ build warnings by preventing use of the deprecated -Ofast flag when building in Release mode.

Changes:

• Update Release-mode compile flag logic to skip -Ofast for Clang versions >= 19.

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[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.07%. Comparing base (0deee81) to head (6c99acb).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6520      +/-   ##
==========================================
- Coverage   93.08%   93.07%   -0.01%     
==========================================
  Files         809      809              
  Lines      256380   256467      +87     
==========================================
+ Hits       238651   238712      +61     
- Misses      17729    17755      +26     

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[nihui]

aha, apple clang still suffers from the deprecation warnings :)

[zhuzeitou]

aha, apple clang still suffers from the deprecation warnings :)

AppleClang 17 is based on Clang 19, but its version number is less than 19.0.
I removed -Ofast for all Clang variants, since -Ofast is equivalent to -O3 -ffast-math in Clang, and the Release build type already provide -O3 and the script appends -ffast-math immediately after.