devtools/bazel-cache: build from source, use docker_push

Change-Id: Ie889372b9a7b439e04c1899c90753349440e727a
diff --git a/.gitignore b/.gitignore
index 34b85ba..6e45050 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,3 @@
 *swp
-bazel-*
+/bazel-*
 .kubectl