Updating build,gradle to generate the support jar dependency dynamically.

This keeps the dependency file up to date with the version of the
plugin.

Change-Id: I9bd34d73740e9be79720f1a4945fa12a8a9266fa

Author: claywilkinson

GoogleSignInPlugin/Assets/GoogleSignIn/Editor/GoogleSignInDependencies.xml

@@ -3,36 +3,11 @@
   <!-- See https://github.com/googlesamples/unity-jar-resolver#usage for
     how to configure dependencies -->
   <androidPackages>
-    <!-- Internal library dependency. -->
-    <androidPackage spec="com.google.signin:google-signin-support:1+">
-      <repositories>
-        <repository>Assets/GoogleSignIn/Editor/m2repository</repository>
-      </repositories>
-    </androidPackage>
-    <!--- Auth  THIS IS ALWAYS REQUIRED -->
-    <!-- The dependency is actually on 10.2, but 10+ is close enough.
-         If you have problems, please change this to a concrete value.
-    -->
     <androidPackage spec="com.google.android.gms:play-services-auth:10+">
       <androidSdkPackageIds>
         <androidSdkPackageId>extra-google-m2repository</androidSdkPackageId>
       </androidSdkPackageIds>
     </androidPackage>
-
-    <!-- IF YOU ARE USING THE GAMES_CONFIG TO SIGN-IN, YOU NEED TO
-           UNCOMMENT THIS DEPENDENCY!!
-
-            This is only used if you need to add play-services-games to your
-            project.
-    -->
-    <!--
-    <androidPackage spec="com.google.android.gms:play-services-games:10+">
-      <androidSdkPackageIds>
-        <androidSdkPackageId>extra-google-m2repository</androidSdkPackageId>
-      </androidSdkPackageIds>
-    </androidPackage>
-    -->
-
   </androidPackages>
 
   <!-- iOS Cocoapod dependencies can be specified by each iosPod element. -->

GoogleSignInPlugin/Assets/GoogleSignIn/Editor/GoogleSignInSupportDependencies.xml.meta

@@ -180,6 +180,27 @@ task import_jarresolver() {
     }
 }
 
+task generate_dependency_xml() {
+  description "Generate the JarResolver dependency file for the support library"
+  dependsOn copy_unity_project
+  doFirst {
+    def xmlFile = file("${pluginProjectPath}/${editorDir}/GoogleSignInSupportDependencies.xml")
+
+    xmlFile << '<?xml version="1.0" encoding="UTF-8" ?>\n'
+    xmlFile << '<dependencies>\n'
+    xmlFile << '<!-- Internal library dependency generated at build time. -->\n'
+    xmlFile << '  <androidPackages>\n'
+    xmlFile << '    <androidPackage spec="com.google.signin:google-signin-support:'
+    xmlFile << "${pluginVersion}\">\n"
+    xmlFile << '      <repositories>\n'
+    xmlFile << '        <repository>Assets/GoogleSignIn/Editor/m2repository</repository>\n'
+    xmlFile << '      </repositories>\n'
+    xmlFile << '    </androidPackage>\n'
+    xmlFile << '  </androidPackages>\n'
+    xmlFile << '</dependencies>\n'
+  }
+}
+
 task generate_manifest(dependsOn: [ 'inject_versionIntoMetaFiles']) {
   description 'Generate a manifest for the files in the plug-in.'
   doLast {
@@ -293,7 +314,7 @@ task package_sample () {
 
 task inject_versionIntoMetaFiles() {
   description 'Inject the version number into the plugin\'s meta files.'
-  dependsOn copy_unity_project, import_jarresolver
+  dependsOn copy_unity_project, generate_dependency_xml, import_jarresolver
   doLast {
     for (fileobj in fileTree("${pluginProjectPath}")) {
       if (fileobj.path.endsWith('.meta')) {