Python fails to validate github.com SSL certificate, unless we first
run a dummy download to force refreshing Windows' CA database.
See: https://bugs.python.org/issue36137
Adapted from patches by Xavier Claessens!
* Install git-lfs as its required now by gst-integration-suites
* Clone gst-build eache time to avoid dated gst-build checkouts
and overwritting .wrap files. Similar to !137
* Split the dockerfile and add a second run stage refresh the
powershell env inbetween calls
* Remove the msys2 workaround as its not needed anymore
