Add a command to push a tag to the repository

The tag is named `v$version` and will thus appear in the tags/releases tabs of the repository, where we can add text explaining new features, API changes, etc.

cranelift/publish-all.sh

@@ -34,7 +34,9 @@ cargo update
 # Note that libraries need to be published in topological order.
 
 echo git commit -a -m "\"Bump version to $version"\"
+echo git tag v$version
 echo git push
+echo git push v$version
 for crate in \
     entity bforest codegen/meta codegen frontend native \
     preopt \