Inform Gradle where to locate pre-installed JDKs

.github/workflows/integ-test-detect-java-toolchains.yml

@@ -80,3 +80,27 @@ jobs:
       run: | 
         grep -q 'Eclipse Temurin JDK 16' output.txt || (echo "::error::Did not detect setup-java installed JDK 16" && exit 1)
         grep -q 'Eclipse Temurin JDK 20' output.txt || (echo "::error::Did not detect setup-java installed JDK 20" && exit 1)
+
+  # Test that predefined JDK detection property is not overwritten by action
+  check-no-overwrite:
+    strategy:
+      matrix:
+        os: ${{fromJSON(inputs.runner-os)}}
+    runs-on: ${{ matrix.os }}
+    steps:
+    - name: Checkout sources
+      uses: actions/checkout@v3
+    - name: Download distribution if required
+      uses: ./.github/actions/download-dist
+    - name: Configure java installations env var in Gradle User Home
+      shell: bash
+      run: | 
+        mkdir -p ~/.gradle
+        echo "org.gradle.java.installations.fromEnv=XXXXX" > ~/.gradle/gradle.properties
+    - name: Setup Gradle
+      uses: ./
+    - name: Check gradle.properties
+      shell: bash
+      run: |
+        cat ~/.gradle/gradle.properties
+        grep -q 'org.gradle.java.installations.fromEnv=JAVA_HOME' && exit 1