[release/6.0] Add alpine to CI for source-build#13074

mthalman merged 3 commits intodotnet:release/6.0.1xxdotnet/installer:release/6.0.1xxfrom

omajid:6.0.1xx-source-build-alpine-ciomajid/dotnet-installer:6.0.1xx-source-build-alpine-ciCopy head branch name to clipboard