build.gradle.kts: moved module-info and java9 related configuration to precompiled script plugins

buildSrc/src/main/kotlin/flatlaf-java9.gradle.kts

@@ -0,0 +1,44 @@
+/*
+ * Copyright 2020 FormDev Software GmbH
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+plugins {
+	java
+}
+
+if( JavaVersion.current() >= JavaVersion.VERSION_1_9 ) {
+	sourceSets {
+		create( "java9" ) {
+			java {
+				setSrcDirs( listOf( "src/main/java9" ) )
+			}
+		}
+	}
+
+	tasks {
+		named<JavaCompile>( "compileJava9Java" ) {
+			sourceCompatibility = "9"
+			targetCompatibility = "9"
+		}
+
+		jar {
+			manifest.attributes( "Multi-Release" to "true" )
+
+			into( "META-INF/versions/9" ) {
+				from( sourceSets["java9"].output )
+			}
+		}
+	}
+}