Compiling DMD/Phobos on OSX (vs linux)

[Nick Sabalausky]

I'm familiar with building DMD/Phobos on linux32/64 (and I assume
freebsd is much the same, aside from having to install GNU make), but I
know OSX is different in that the 32/64-bits bins are combined. I don't
have access to a modern OSX machine ATM, but I might have a little
bit of time with one tomorrow (I'm pretty sure it's either 10.6 or 10.7
- I know it's a Core i7 laptop FWIW).

So I wanted to ask, is there anything I should know about doing a full
build of DMD/Phobos on OSX? Is it just like doing a 32-bit-only or
64-bit-only build on linux, but just without using -m32/-m64? Or do I
do one arch and then the other? Or does it differ between the different
components (dmd/druntime/phobos)? Etc. And are there any special
OSX-only prerequisites?