This is already achieved by removing //build/config:no_rtti config.

Change-Id: Id5dd6ac5d054a959ce05b1d29148e5ef7d1c6a5c

Delete the convert_bazel script which is no-longer used.
Also, remove an unused variable that was causing build troubles in
Fuchsia.

Change-Id: I6639bcd120d340adca1b6a32b51e90011344d087