chore: pin openstack deps (#391)

* chore: pin openstack deps

This commit adds infrastructure to pin OpenStack images which are
tagged by release in order to ensure the exact image is used in
a specific Atmosphere release.

It also adds an Earthfile which can automatically execute the
pinning.

* fix: allow for missing groups
diff --git a/galaxy.yml b/galaxy.yml
index 62a71eb..ac777b8 100644
--- a/galaxy.yml
+++ b/galaxy.yml
@@ -32,6 +32,7 @@
 issues: https://github.com/vexxhost/atmosphere/issues
 build_ignore:
   - .github
+  - build
   - ci
   - cmd
   - docs