Parallelize builds
diff --git a/ci/build-project-matrix b/ci/build-project-matrix
new file mode 100755
index 0000000..29a7e8d
--- /dev/null
+++ b/ci/build-project-matrix
@@ -0,0 +1,12 @@
+#!/usr/bin/env python3
+
+import glob
+import sys
+import json
+
+
+json.dump(
+    sorted([r.split("/")[-1] for r in glob.glob("images/openstack/projects/*")]),
+    sys.stdout,
+    separators=(",", ":"),
+)