Fix incorrect repo path in mainTemplate.gradle when export gradle project

When Custom Gradle Template and Export Gradle Project setting in Unity are
enabled, Android Resolver should inject absolute path to the generated
local maven repo.

Bug: 158040316

Fixed #366

Change-Id: I0d21705aeb4f7b0dacc58f3be5f26fe9c72c1bd2

Author: chkuang-g

source/AndroidResolver/src/PlayServicesResolver.cs

@@ -1999,12 +1999,20 @@ internal static IList<string> GradleMavenReposLines(ICollection<Dependency> depe
                         new Dictionary<string, List<string>>();
                 foreach (var repoAndSources in GetRepos(dependencies: dependencies)) {
                     string repoUri;
-                    if (repoAndSources.Key.StartsWith(projectFileUri) && !exportEnabled) {
+                    if (repoAndSources.Key.StartsWith(projectFileUri)) {
                         var repoPath = repoAndSources.Key.Substring(projectFileUri.Length + 1);
                         repoPath = FileUtils.PosixPathSeparators(
                             FileUtils.ReplaceBaseAssetsOrPackagesFolder(
                                 repoPath, GooglePlayServices.SettingsDialog.LocalMavenRepoDir));
-                        repoUri = String.Format("(unityProjectPath + \"/{0}\")", repoPath);
+
+                        // If "Export Gradle Project" setting is enabled, gradle project expects
+                        // absolute path.
+                        if (exportEnabled) {
+                            repoUri = String.Format("\"{0}\"",
+                                                    Path.Combine(projectFileUri, repoPath));
+                        } else {
+                            repoUri = String.Format("(unityProjectPath + \"/{0}\")", repoPath);
+                        }
                     } else {
                         repoUri = String.Format("\"{0}\"", repoAndSources.Key);
                     }