Compiling mod_mono under Debian Sarge

As part of re-enabling Mono I encountered a strange error when I was compiling mod_mono:

 apxs:Error: no config variable PREFIX

The solution (via Gonzalo) is to modify the Makefile slightly:

 $ sed -i -e 's/ -S PREFIX="$(prefix)"//' src/Makefile.in

Do this before you ./configure and everything then works.