Add .repo/ to .gitignore

Useful for anyone who set up repo with this project as the root.

Signed-off-by: Xo Wang <xow@google.com>
Change-Id: I68e63bfd2f3cdea607696b02cbc443324b6e9896
diff --git a/.gitignore b/.gitignore
index 48652c2..316a0eb 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,4 @@
 build*/*
 customrc
 *.sw?
+.repo/