My snow leopard build machine has clang 4.0 (it also has libc++, is it required or is the system libstdc++ OK?). It's an 8-core Mac Pro, so the build shouldn't be that long. I think 10.6-10.8 deserve a decent and secure browser, since these systems were dropped by Mozilla this year. I'll start by following the build instructions for Leopard, and see where it fails. If you have notes specific to Snow Leopard, the best is perhaps to put this in the same wiki page.
Do you have a setup or build script that you use for the Leopard build? I volunteer to try out building for SL (i386/x86_64). I would most certainly use clang-3.4, which is the last one with full compatibility with the system's libstdc++. Using a more recent GCC or clang means it would either depend on another libstdc++, or on libc++