How to build Mono from cvs on OSX
In mono_root/mono/mini comment out this line in Makefile.am: libmono_la_LDFLAGS=$(monoldflags)
Then rerun autogen.sh from the mono root directory. You need to install a current version of libgc. It's called the Boehm GC for those that have never heard of it.
Configure with
./configure --with-gc=boehm
It's not a good idea to specify a non-default location because if you don't install to that place again, the next go around might because you to get "corlib out of sync with runtime errors"