Don't clone repositories for APKs.

On Android, the chromium-webview repository is 2.5G but holds only
~200mb of data at head.

Change-Id: I68641452aab2131a504c9c8fe3326710ba64d324

android.json

diff --git a/android.json b/android.json
index 98cead6..57b736e 100644
--- a/android.json
+++ b/android.json
@@ -4,11 +4,15 @@
     "Clone": false
   },
   {
-    "File": ".*mk$",
+    "File": ".*\\.mk$",
     "Clone": false
   },
   {
-    "File": ".*bp$",
+    "File": ".*\\.bp$",
     "Clone": false
-  }
+  },
+  {
+    "File": ".*\\.apk$",
+    "Clone": false,
+  },
 ]