Explicitly require ${LOCALBASE}/lib/libfreetype to be present at the build time,
because WM may fail to build if XFree86-4's version of libfreetype.so.6 is
detected and freetype2 port is not installed (XFree86 doesn't install any
freetype's header files). This is temporarly workaround until jmz will fix
XFree86-4 properly.

Prompted by: Mister X <scanner@jurai.net>