I'm using the Debian package creator too, and as far as I know, "-DENABLE_MONITOR=on" is a default with this option (see line 39 of ./extra/make_debian_package).
Have you tried "hiawatha -v" to verify the build time options? Here is what mines say:
Hiawatha v8.7, cache, IPv6, Monitor, reverse proxy, SSL, Tomahawk, URL toolkit, XSLT
Copyright (C) by Hugo Leisink <hugo@leisink.net>