CI: fix dir jumps in build_if_needed
In !401 (merged), we moved pushd/popd to fix renderDockerfile, but it turns
out that we need them inside the if block as well, due to tag_and_push
Un-break pushing tags
Edited by Jason Plum
In !401 (merged), we moved pushd/popd to fix renderDockerfile, but it turns
out that we need them inside the if block as well, due to tag_and_push
Un-break pushing tags