TBR: mojo.shared: Add '/.jiri' to .gitignore in all repos.

Change-Id: Ic09f0c4cf816a13e4da5b605d0bcd1dc66569a50
MultiPart: 15/28
PresubmitTest: none
diff --git a/.gitignore b/.gitignore
index b7e2fde..c2296ef 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1 +1,3 @@
+/.jiri
+#TODO(nlacasse): Get rid of .v23 below once v23->jiri transition is complete.
 /.v23
\ No newline at end of file