Add build rule back for markupsafe.

The markupsafe lib wasn't in the master-without-vendor branch due to
there is merge conflict master -> master-without-vendor that has not
been resolved. But markupsafe is merged in master-without-vendor branch
now. ag/12545538. So add the build rule back.
For the details of merging conflict: b/167204216

Change-Id: Ice72543e236a23a14c458f0dff211db7f31d12f1