fix gcc build for missing _mm512_set_epi16 intrinsic

[nihui]

No description provided.

[tencent-adm]

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[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.48%. Comparing base (a5392dd) to head (0b20ba3).
⚠️ Report is 3 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6782      +/-   ##
==========================================
- Coverage   95.49%   95.48%   -0.01%     
==========================================
  Files         946      946              
  Lines      410295   410063     -232     
==========================================
- Hits       391791   391530     -261     
- Misses      18504    18533      +29     

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