CI: install_pmb: use git clone, not tarball (!980)

GitLab disabled downloads of tarballs currently, because it was being
exploited for DoS agains their infrastructure. Work around this by using
git clone for now. I've thought about using --depth=1, but that would
break the ability to choose different branches.

Related: https://status.gitlab.com

.gitlab-ci/install_pmbootstrap.sh

@@ -7,7 +7,7 @@
 tag="master"
 
 # Get download URL and pmaports path
-url="https://gitlab.com/postmarketOS/pmbootstrap/-/archive/$tag/pmbootstrap-$tag.tar.bz2"
+url="https://gitlab.com/postmarketOS/pmbootstrap.git"
 pmaports="$(cd $(dirname $0)/..; pwd -P)"
 
 # Set up depends and binfmt_misc
@@ -25,9 +25,8 @@ echo 'pmos ALL=(ALL) NOPASSWD: ALL' >> /etc/sudoers
 # Download pmbootstrap (to /tmp/pmbootstrap)
 echo "Downloading pmbootstrap ($tag): $url"
 cd /tmp
-wget -q -O "pmb.tar.bz2" "$url"
-tar -xf "pmb.tar.bz2"
-mv pmbootstrap-* pmbootstrap
+git clone -q "$url"
+git -C pmbootstrap checkout -q "$tag"
 
 # Install to $PATH and init
 ln -s /tmp/pmbootstrap/pmbootstrap.py /usr/local/bin/pmbootstrap