Use release-tools Module for Mage Build

[tri-adam]

Use github.com/sylabs/release-tools, replacing github.com/sylabs/sif/v2/internal/pkg/git and simplifying the logic in magefile.go.

[codecov-commenter]

Codecov Report

Merging #158 (b97cb95) into master (f9e58a4) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #158   +/-   ##
=======================================
  Coverage   75.27%   75.27%           
=======================================
  Files          28       28           
  Lines        2419     2419           
=======================================
  Hits         1821     1821           
  Misses        459      459           
  Partials      139      139           

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[dtrudg]

LGTM