Roll to android build plugin 2.2.0-rc2.

Change-Id: I930c6558bf6f2448c05ef2ef04237e7dc1bcd8e3
diff --git a/build.gradle b/build.gradle
index dd30dfb..444a362 100644
--- a/build.gradle
+++ b/build.gradle
@@ -14,7 +14,7 @@
         maven { url "../../prebuilts/maven_repo/android" }
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:2.2.0-rc1'
+        classpath 'com.android.tools.build:gradle:2.2.0-rc2'
     }
 }