Configure target java version alongside gradle toolchain (nextflow-io…

…#5676)

build.gradle

@@ -67,20 +67,18 @@ allprojects {
     apply plugin: 'jacoco'
 
     java {
+        // these settings apply to all jvm tooling, including groovy
         toolchain {
             languageVersion = JavaLanguageVersion.of(21)
         }
+        sourceCompatibility = 17
+        targetCompatibility = 17
     }
 
     compileJava {
         options.release.set(17)
     }
 
-    tasks.withType(GroovyCompile) {
-        sourceCompatibility = 17
-        targetCompatibility = 17
-    }
-
     idea {
         module.inheritOutputDirs = true
     }