current way of gradle cache, use javac release flag

.github/workflows/gradle.yml

@@ -30,25 +30,15 @@ jobs:
       id: ci-env
       uses: FranzDiebold/github-env-vars-action@v2
 
-    - name: Set up Java
-      uses: actions/setup-java@v2
+    - name: Set up java
+      uses: actions/setup-java@v2.5.0
       with:
-        distribution: 'temurin'
         java-version: ${{ matrix.java }}
-
-    - name: Cache Gradle packages
-      # speed up the build by caching dependencies, downloaded versions
-      uses: actions/cache@v2
-      with:
-        path: |
-          ~/.gradle/caches
-          ~/.gradle/wrapper
-        key: ${{ runner.os }}-gradle-${{ hashFiles('**/*.gradle*', '**/gradle-wrapper.properties') }}
-        restore-keys: |
-          ${{ runner.os }}-gradle-
+        distribution: temurin
+        cache: gradle
 
     - name: Build with Gradle
-      run: ./gradlew build
+      run: gradle clean build -PjavacRelease=${{ matrix.java }}
 
     - name: SHA256
       if: matrix.upload

build.gradle.kts

@@ -1,3 +1,8 @@
+//    permits to start the build setting the javac release parameter, no parameter means build for java8:
+// gradle clean build -PjavacRelease=8
+// gradle clean build -PjavacRelease=17
+val javacRelease = (project.findProperty("javacRelease") ?: "8") as String
+
 plugins {
   id("fr.brouillard.oss.gradle.jgitver") version "0.9.1"
   id("jacoco")
@@ -38,9 +43,12 @@ jgitver {
   useGitCommitID = true
 }
 
-java {
-  sourceCompatibility = JavaVersion.VERSION_1_8
-  targetCompatibility = JavaVersion.VERSION_1_8
+tasks.compileJava {
+  if (JavaVersion.current().isJava8) {
+    java.targetCompatibility = JavaVersion.VERSION_1_8
+  } else {
+    options.release.set(Integer.parseInt(javacRelease))
+  }
 }
 
 tasks.withType<Jar> {