.github: Add workflow step to build & test

Previously we were missing a straightforward 'make' workflow, so this
meant that we could merge commits that would break the build on main.
Fix this by adding such a step to the main github workflow that runs on
every PR and commit into the tree.

Signed-off-by: Joe Stringer <joe@cilium.io>

Author: joestringer

.github/workflows/build-image.yaml

@@ -32,6 +32,10 @@ jobs:
         with:
           persist-credentials: false
 
+      - name: Build and test
+        run: |
+          make
+
       - name: Docker meta
         id: meta
         uses: docker/metadata-action@8e5442c4ef9f78752691e2d8f8d19755c6f78e81 # v5.5.1