Check ruby gem and SQLite3 for FTS3 or FTS4 support
The documentation states:


  Note that enabling FTS3 also makes FTS4 available. There is not a
  separate SQLITE_ENABLE_FTS4 compile-time option. A build of SQLite
  either supports both FTS3 and FTS4 or it supports neither.


So if FTS3 works, so does FTS4.

Doesn't look like it's possible to tell what options sqlite was compiled with according to this SO answer.