Add gclient files to gitignore

This Cl updates the .gitignore with the .gclient and .gclient_entries
files.

Bug: tint:12
Change-Id: I645016ca83396c0616f2ad3f69d2ce510be59b53
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/16580
Reviewed-by: Ryan Harrison <rharrison@chromium.org>
diff --git a/.gitignore b/.gitignore
index ed1481c..0e382d7 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,5 +1,7 @@
-.vscode
 .DS_Store
+.gclient
+.gclient_entries
+.vscode
 build
 out
 third_party/cpplint