Try self-hosted compilation

Author: zauguin

.github/workflows/tests.yaml

@@ -34,7 +34,7 @@ jobs:
   # create three jobs which only differ in minimal elements.
   # For tags we do not run this since we run the release job instead.
   l3build:
-    runs-on: ubuntu-latest
+    runs-on: self-hosted
     strategy:
       fail-fast: false
       matrix: