Allow bin empty directory to be checked out.

diff --git a/bin/.gitignore b/bin/.gitignore
new file mode 100644
index 0000000..0904da3
--- /dev/null
+++ b/bin/.gitignore
@@ -0,0 +1,6 @@
+# Ignore everything in this directory since we don't want to commit
+# binaries:
+*
+# But don't ignore this file itself:
+!.gitignore
+