Add some more things that should be ignored to .gitignore

Reviewed at https://codereview.appspot.com/6498119/

Review URL: https://codereview.appspot.com/6503107

git-svn-id: http://skia.googlecode.com/svn/trunk@5509 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/.gitignore b/.gitignore
index 895cc0c..cac3278 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,6 @@
 /out/
 /third_party/externals/
+/gyp/build/
+/xcodebuild/
+.DS_Store
+.gclient*