ci: build static musl binaries for x86_64 and aarch64

[sylvestre]

Closes #387.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.86%. Comparing base (865ab09) to head (43b52b4).
⚠️ Report is 14 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #741      +/-   ##
==========================================
+ Coverage   91.83%   91.86%   +0.02%     
==========================================
  Files          35       35              
  Lines        7129     7153      +24     
  Branches      375      375              
==========================================
+ Hits         6547     6571      +24     
  Misses        437      437              
  Partials      145      145              

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[codspeed-hq]

Merging this PR will not alter performance

✅ 20 untouched benchmarks

---

_{Comparing sylvestre:musl-static-binaries-387 (43b52b4) with main (b637fb1)}

[github-actions]

Commit 43b52b4 has test result changes:

bfs testsuite:

Test results comparison:
  Current:   TOTAL: 315 / PASSED: 267 / FAILED: 42 / SKIPPED: 6
  Reference: TOTAL: 314 / PASSED: 267 / FAILED: 41 / SKIPPED: 6

Changes from main branch:
  TOTAL: +1
  PASSED: +0
  FAILED: +1

New test failures (1):
  - gnu/files0_from_ok