Set GitSHA when using goreleaser

[johnSchnake]

What this PR does / why we need it:
The makefile sets this flag but goreleaser was not configured
to do so.

Which issue(s) this PR fixes
Fixes #748

Special notes for your reviewer:
If you download/install https://github.com/goreleaser/goreleaser you can run the following goreleaser command to test it out (for darwin; you can specify the linux path if you need that version):

goreleaser --skip-publish --skip-validate --rm-dist && ./dist/darwin_amd64/sonobuoy version

Release note:

Fixed a bug which caused releases to not list the GitSHA they were built from.

[codecov-io]

Codecov Report

Merging #750 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #750   +/-   ##
=======================================
  Coverage   42.59%   42.59%           
=======================================
  Files          70       70           
  Lines        4029     4029           
=======================================
  Hits         1716     1716           
  Misses       2208     2208           
  Partials      105      105

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