reduce warnings inside flutter.groovy file #2 (flutter#155628)

follow up for : [flutter#152073](flutter#152073)

Author: AbdeMohlbi

packages/flutter_tools/gradle/src/main/groovy/flutter.groovy

@@ -1423,15 +1423,15 @@ class FlutterPlugin implements Plugin<Project> {
                         filename += "-${buildModeFor(variant.buildType)}"
                         project.copy {
                             from new File("$outputDirectoryStr/${output.outputFileName}")
-                            into new File("${project.buildDir}/outputs/flutter-apk")
+                            into new File("${project.layout.buildDirectory.dir("outputs/flutter-apk").get()}")
                             rename {
                                 return "${filename}.apk"
                             }
                         }
                     }
                 }
                 // Copy the native assets created by build.dart and placed here by flutter assemble.
-                String nativeAssetsDir = "${project.buildDir}/../native_assets/android/jniLibs/lib/"
+                String nativeAssetsDir = "${project.layout.buildDirectory.dir("../native_assets/android/jniLibs/lib").get()}/"
                 project.android.sourceSets.main.jniLibs.srcDir(nativeAssetsDir)
             }
             configurePlugins(project)