installer: test writable install directory

[glensc]

The current script requires sudo, even /usr/local/bin is writable for a non-privileged user

[derek]

Thank you for your contribution. I've just checked and your commit doesn't appear to be signed-off. That's something we need before your Pull Request can be merged. Please see our contributing guide.
Tip: if you only have one commit so far then run: git commit --amend --signoff and then git push --force.

[codecov]

Codecov Report

Merging #780 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #780   +/-   ##
=======================================
  Coverage   32.36%   32.36%           
=======================================
  Files          63       63           
  Lines        4944     4944           
=======================================
  Hits         1600     1600           
  Misses       3212     3212           
  Partials      132      132

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[rberrelleza]

CI failure is unrelated, I'll fix it in a separate PR.

[rberrelleza]

Thanks for the contribution @glensc !