[release-19.0] Update env.sh so that is does not error when running on Mac (#15835)

[vitess-bot]

Description

This is a backport of #15835

[vitess-bot]

Review Checklist

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General

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 67.46%. Comparing base (15ad36f) to head (15ad36f).

❗ Current head 15ad36f differs from pull request most recent head a9940b8. Consider uploading reports for the commit a9940b8 to get more accurate results

Additional details and impacted files

@@              Coverage Diff              @@
##           release-19.0   #15915   +/-   ##
=============================================
  Coverage         67.46%   67.46%           
=============================================
  Files              1560     1560           
  Lines            192822   192822           
=============================================
  Hits             130084   130084           
  Misses            62738    62738           

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