Hithomelabs/HomeLabDocker#76: Fix Gradle build failure — replace setup-java with Alpine JDK package

The actions/setup-java@v4 step downloads a glibc-compiled JDK (Temurin)
which cannot execute on Alpine's musl libc. Replace with Alpine's native
openjdk17-jdk package via apk, which is compiled for musl and works
correctly with gradlew.

.gitea/workflows/test-ci-runner.yml

@@ -1,5 +1,7 @@
 name: Test CI Runner Image
 on:
+  push:
+    branches: [test, main]
   workflow_dispatch:
 
 jobs:
@@ -10,11 +12,10 @@ jobs:
     steps:
       - uses: actions/checkout@v4
 
-      - name: Install JDK (JRE-only image)
-        uses: actions/setup-java@v4
-        with:
-          java-version: 17
-          distribution: temurin
+      - name: Install JDK (musl-native, Alpine package)
+        run: |
+          apk add --no-cache openjdk17-jdk
+          echo "JAVA_HOME=/usr/lib/jvm/java-17-openjdk" >> "$GITHUB_ENV"
 
       - name: Verify tools
         run: |