Add experimental CI using Kas+GitLab

Add kas scripts that generic to test builds, and a GitLab CI runner.

This is mainly a cut-down copy of what is in the master/gatesgarth
branches with the following changes:

- Just the BSPs that are in the Dunfell release, obviously
- No clang testing. There are patches in master that can be backported
  if required.
- Added testing of the armgcc-9.2 compiler. This is currently broken for
  some configurations in master and the testing will be forward-ported
  when it passes.

Change-Id: I9c2a4f66318b3ccc066d423f3533202ee33f0c9d
Signed-off-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Jon Mason <jon.mason@arm.com>

kas/check-machine-coverage

@@ -0,0 +1,26 @@
+#! /usr/bin/env python3
+
+from pathlib import Path
+import sys
+
+metaarm = Path.cwd()
+
+if metaarm.name != "meta-arm":
+    print("Not running inside meta-arm")
+    sys.exit(1)
+
+# All machine configurations
+machines = metaarm.glob("meta-*/conf/machine/*.conf")
+machines = set(p.stem for p in machines)
+
+# All kas files
+kas = metaarm.glob("kas/*.yml")
+kas = set(p.stem for p in kas)
+
+missing = machines - kas
+print(f"The following machines are missing: {', '.join(sorted(missing))}.")
+
+covered = len(machines) - len(missing)
+total = len(machines)
+percent = int(covered / total * 100)
+print(f"Coverage: {percent}%")