opm: build fully static opm binaries/images

[joelanford]

Description of the change:
We typically compile opm with --ldflags=-extldflags=-static, but that was missed when transposing the Makefile into the opm image's goreleaser configuration.

This PR adds that flag to goreleaser builds and updates the base image of quay.io/operator-framework/opm from gcr.io/distroless/base:debug to gcr.io/distroless/static:debug

Motivation for the change:
Fix an issue with opm binary builds, decrease the size of the opm image, and decrease the surface area for vulnerabilities.

Closes #777

Reviewer Checklist

• Implementation matches the proposed design, or proposal is updated to match implementation
• Sufficient unit test coverage
• Sufficient end-to-end test coverage
• Docs updated or added to /docs
• Commit messages sensible and descriptive

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: joelanford

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[codecov]

Codecov Report

Merging #778 (12607d2) into master (a3253eb) will not change coverage.
The diff coverage is n/a.

❗ Current head 12607d2 differs from pull request most recent head 2ab3160. Consider uploading reports for the commit 2ab3160 to get more accurate results

@@           Coverage Diff           @@
##           master     #778   +/-   ##
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  Coverage   50.90%   50.90%           
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  Files         102      102           
  Lines        8753     8753           
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  Hits         4456     4456           
  Misses       3458     3458           
  Partials      839      839           

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[timflannagan]

/lgtm