CI: Run tests

The tests don't require access to Hexagon hardware, they currently pass,
and running them will provide a better assurance against regressions.

Signed-off-by: J. Neuschäfer <j.ne@posteo.net>

.github/workflows/build.yaml

@@ -1,4 +1,4 @@
-name: Buildtest
+name: Build+test
 
 on:
   pull_request:
@@ -27,3 +27,7 @@ jobs:
         run: |
           meson setup build
           ninja -C build
+
+      - name: run tests
+        run: |
+          ninja -C build test