refactor: use custom prebuild llvm distribution on ubuntu

[baszalmstra]

No description provided.

[codecov]

Codecov Report

Merging #260 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #260   +/-   ##
=======================================
  Coverage   78.50%   78.50%           
=======================================
  Files         215      215           
  Lines       12709    12709           
=======================================
  Hits         9977     9977           
  Misses       2732     2732           

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[baszalmstra]

Closing this, we are going to keep it this way. But modify the artifact stage instead to build in a docker container that does static linking.