CI: make sure devices that support kernel updates install the script (MR 2215)

To prevent accidental bricks, postmarketos-update-kernel is not
installed by default. If it works for your device and you've added the
deviceinfo variable, you also need to depend on the package for the
updates to actually happen.

[ci:skip-build] already built successfully in CI

.gitlab-ci/testcases/test_device.py

@@ -57,6 +57,14 @@ def test_aports_device(args):
         if "!archcheck" not in apkbuild["options"]:
             raise RuntimeError("!archcheck missing in options= line: " + path)
 
+        if deviceinfo["flash_kernel_on_update"] == "true" \
+                and "postmarketos-update-kernel" not in apkbuild["depends"]:
+            raise RuntimeError(
+                "Deviceinfo indicates this device supports automatic kernel"
+                " flashing on update, but doesn't depend on"
+                " 'postmarketos-update-kernel'. Please add the missing"
+                " dependency.")
+
 
 def test_aports_device_kernel(args):
     """