ignore build directories

Change-Id: I842549ebb91fc27043046c21b85c4d96d40ebff4
diff --git a/.gitignore b/.gitignore
index 4638497..ca68365 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,4 @@
 /ring-daemon
 env.sh
 obj/
+android-toolchain-*/