Add plugin to update license in proprietary sdks. (#2416)

Author: rlazo

buildSrc/src/main/java/com/google/firebase/gradle/plugins/FirebaseProprietaryLibraryPlugin.kt

@@ -0,0 +1,36 @@
+// Copyright 2021 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.firebase.gradle.plugins
+
+import org.gradle.api.Plugin
+import org.gradle.api.Project
+import org.gradle.kotlin.dsl.apply
+
+class FirebaseProprietaryLibraryPlugin : Plugin<Project> {
+    override fun apply(project: Project) {
+        project.apply(plugin = "FirebaseLibraryPlugin")
+
+        val library = project.extensions.getByType(FirebaseLibraryExtension::class.java)
+        library.publishSources = false
+        library.customizePom {
+            licenses {
+                license {
+                    name.set("Android Software Development Kit License")
+                    url.set("https://developer.android.com/studio/terms.html")
+                }
+            }
+        }
+    }
+}