Add android build cache to Travis

SUPERCILEX · SUPERCILEX · commit 129c34c1dedc · 2017-01-03T18:08:16.000-08:00
Signed-off-by: Alex Saveau &lt;saveau.alexandre@gmail.com&gt;
diff --git a/.travis.yml b/.travis.yml
@@ -9,6 +9,7 @@ cache:
   directories:
     - $HOME/.gradle/caches/
     - $HOME/.gradle/wrapper/
+    - $HOME/.android/build-cache
 android:
   components:
     - tools
