gradle: kts dsl (#1845)

* gradle: kts dsl

* deob: Fix tests

* gradle: Convert fernflower plugin to kotlin

buildSrc/src/main/kotlin/FernflowerTask.kt

@@ -0,0 +1,30 @@
+import org.gradle.api.DefaultTask
+import org.gradle.api.tasks.TaskAction
+import org.jetbrains.java.decompiler.main.decompiler.ConsoleDecompiler
+import java.io.File
+
+open class FernflowerTask: DefaultTask() {
+
+    var extraArgs: List<String>? = null
+    var inputJar: String? = null
+    var outputDir: String? = null
+
+    fun getInputJar(): File {
+        return project.file(inputJar ?: project.buildDir.toString() + "/libs/" + project.name + '-' + project.version + ".jar")
+    }
+
+    fun getOutputDir(): File {
+        return project.file(outputDir ?: project.buildDir.toString() + "/decompiled-sources")
+    }
+
+    @TaskAction
+    fun decompile() {
+        getOutputDir().mkdirs()
+        val args = mutableListOf(getInputJar().toString(), getOutputDir().toString())
+        if (extraArgs != null) {
+            args.addAll(extraArgs!!)
+        }
+
+        ConsoleDecompiler.main(args.toTypedArray())
+    }
+}