Add cargoClean gradle task

plugin/src/main/kotlin/com/nishtahir/CargoCleanTask.kt

@@ -0,0 +1,40 @@
+package com.nishtahir;
+
+import com.android.build.gradle.*
+import org.apache.tools.ant.taskdefs.condition.Os
+import org.gradle.api.DefaultTask
+import org.gradle.api.GradleException
+import org.gradle.api.Project
+import org.gradle.api.logging.LogLevel
+import org.gradle.api.tasks.Input
+import org.gradle.api.tasks.Optional
+import org.gradle.api.tasks.TaskAction
+import java.io.ByteArrayOutputStream
+import java.io.File
+
+open class CargoCleanTask : DefaultTask() {
+
+    @Suppress("unused")
+    @TaskAction
+    fun clean() = with(project) {
+        extensions[CargoExtension::class].apply {
+            val theCommandLine = mutableListOf(this.cargoCommand)
+            theCommandLine.add("clean")
+            project.exec { spec ->
+                val cargoExtension = this 
+                with(spec){
+                    val module = File(cargoExtension.module!!)
+                    if (module.isAbsolute) {
+                        workingDir = module
+                    } else {
+                        workingDir = File(project.project.projectDir, module.path)
+                    }
+
+                    workingDir = workingDir.canonicalFile
+                    standardOutput = System.out
+                    commandLine = theCommandLine
+                }
+            }
+        }
+    }
+}

plugin/src/main/kotlin/com/nishtahir/RustAndroidPlugin.kt

@@ -307,5 +307,11 @@ open class RustAndroidPlugin : Plugin<Project> {
             targetBuildTask.dependsOn(generateLinkerWrapper)
             buildTask.dependsOn(targetBuildTask)
         }
+
+        val cleanTask = tasks.maybeCreate("cargoClean",
+                CargoCleanTask::class.java).apply {
+            group = RUST_TASK_GROUP
+            description = "Deletes the target directory."
+        }
     }
 }