C front-end: GCC >= 12 support __builtin_shufflevector

[tautschnig]

This used to be Clang-only, but is now also supported by GCC.

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• Regression or unit tests are included, or existing tests cover the modified code (in this case I have detailed which ones those are in the commit message).
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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (5bce1c3) 79.69% compared to head (74ecb26) 79.69%.

❗ Current head 74ecb26 differs from pull request most recent head 3a0cc1a. Consider uploading reports for the commit 3a0cc1a to get more accurate results

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #8170      +/-   ##
===========================================
- Coverage    79.69%   79.69%   -0.01%     
===========================================
  Files         1680     1680              
  Lines       195239   195237       -2     
===========================================
- Hits        155602   155600       -2     
  Misses       39637    39637              

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