Add flag --ignore-zipalign to not fail when zipalign is not found
Add flag --ignore-zipalign to not fail when zipalign is not found

Summary:
As requested a while back: http://www.facebook.com/groups/847849098618209/permalink/957053884364396/?comment_id=957061427696975&reply_comment_id=957061887696929
I'm making redex fail when zipalign is not found and adding a flag to ignore the error.

Reviewed By: minjang

Differential Revision: D5259770

fbshipit-source-id: bd8f326fe0872cd14cfb79b2828dace7e50bb5e9

facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex