Rework the lombok gradle task to use CLI

This allows us to also specify the BuildConfig directory. Without this,
it is not included in the sources and an annoying warning pops up every
time.

Author: rubengees

library/build.gradle

@@ -28,16 +28,27 @@ dependencies {
     testImplementation deps.privateConstructor
 }
 
-task delombok(dependsOn: compileJava) {
+task delombok(type: JavaExec, dependsOn: compileJava) {
+    def buildConfigInputDir = "$buildDir/gen/buildconfig/src/main"
+
     ext.outputDir = 'build/delombok'
+    outputs.dir(outputDir)
+    inputs.dir(buildConfigInputDir)
+
+    args += "delombok"
 
-    doLast {
-        ant.taskdef(name: 'delombok', classname: 'lombok.delombok.ant.Tasks$Delombok',
-                classpath: configurations.compileOnly.asPath)
+    sourceSets.main.java.srcDirs.each {
+        inputs.dir(it)
 
-        ant.delombok(encoding: 'UTF-8', from: 'src/main/java', to: ext.outputDir,
-                classpath: configurations.compileClasspath.asPath)
+        args += it
     }
+
+    args += buildConfigInputDir
+    args += "--target=$outputDir"
+    args += "--classpath=$configurations.compileClasspath.asPath"
+
+    classpath configurations.compileOnly.asPath
+    main = "lombok.launch.Main"
 }
 
 buildConfig {