update legacy project

.ci/legacy_project/README.md

@@ -55,3 +55,5 @@ and then deleting everything but `android/` from it:
   from version 1.9.0 to 2.1.0. If a user runs into an error with the AGP version,
   the warning is clear on how to upgrade the version to one that we support.
 - Modifies `gradle.properties` to not set android.enableJetifier=true.
+- Update `app/build.gradle` to enable library desugaring to support
+  `interactive_media_ads` plugin.

.ci/legacy_project/all_packages/android/app/build.gradle

@@ -26,6 +26,10 @@ android {
     namespace = "com.example.all_packages"
     compileSdkVersion flutter.compileSdkVersion
 
+    compileOptions {
+      coreLibraryDesugaringEnabled true
+    }
+
     defaultConfig {
         applicationId "com.example.all_packages"
         minSdkVersion flutter.minSdkVersion
@@ -44,3 +48,7 @@ android {
 flutter {
     source '../..'
 }
+
+dependencies {
+  coreLibraryDesugaring 'com.android.tools:desugar_jdk_libs:2.1.5'
+}