[release/8.0.3xx] Stop building source-build in non-1xx branches#51251

NikolaMilosavljevic merged 1 commit intorelease/8.0.3xxdotnet/sdk:release/8.0.3xxfrom

backport/pr-50888-to-release/8.0.3xxdotnet/sdk:backport/pr-50888-to-release/8.0.3xxCopy head branch name to clipboard