Apache mod_rewrite is supported by default in the Dreamhost shared hosting configuration. sqlite is supported by default in the Dreamhost shared hosting configuration. If you require "builit-in" PHP sqlite, select PHP5 as the version of php to run when setting up a fully hosted domain. Otherwise, sqlite is available from the shell command line for scripting purposes, or via the installed perl DBD: module.
It is already done for you if you select PHP5 for use on your domain, are working from the shell, or are using perl (via the module) as described above.
Note (from the php.net Manual):