Only treat warnings as errors when compiling with Java 17

buildSrc/src/main/java/org/springframework/boot/build/JavaConventions.java

@@ -202,11 +202,17 @@ class JavaConventions {
 				compile.setSourceCompatibility(SOURCE_AND_TARGET_COMPATIBILITY);
 				compile.setTargetCompatibility(SOURCE_AND_TARGET_COMPATIBILITY);
 			}
-			args.addAll(Arrays.asList("-Werror", "-Xlint:unchecked", "-Xlint:deprecation", "-Xlint:rawtypes",
+			else if (buildingWithJava17(project)) {
-					"-Xlint:varargs"));
+				args.addAll(Arrays.asList("-Werror", "-Xlint:unchecked", "-Xlint:deprecation", "-Xlint:rawtypes",
+						"-Xlint:varargs"));
+			}
 		});
 	}
 
+	private boolean buildingWithJava17(Project project) {
+		return !project.hasProperty("toolchainVersion") && JavaVersion.current() == JavaVersion.VERSION_17;
+	}
+
 	private void configureSpringJavaFormat(Project project) {
 		project.getPlugins().apply(SpringJavaFormatPlugin.class);
 		project.getTasks().withType(Format.class, (Format) -> Format.setEncoding("UTF-8"));