We now have a universal build that contains 32 and 64-bit binaries for Intel CPUs, instead of PowerPC & Intel 32-bit. This is for all branches except Firefox 3.5 and 3.6, and is based on all the work Josh Aas et. al. have done getting the 64-bit build working nicely, plus the decision to drop PowerPC support for Firefox 4.0.
The new universal build defaults to running 32-bit on Leopard (10.5), and 64-bit on Snow Leopard (10.6). Anyone who has been getting nightly updates for the old universal and also has an Intel processor will be moved over to the new one.
For those of you paying attention to TinderBoxPushLog there is no longer a B for OS X opt, and the B for OS X64 opt is where the new universal build is happening. We do talos and optimized unittest on the new universal build, running it 32-bit on 10.5 and 64bit on 10.6. There are still two debug builds – OS X debug is 32-bit and the unit tests run on 10.5, while OS X64 debug is a 64-bit build tested on 10.6. The debug mochitest-other for the 32-bit build has been disabled due to a packaging problem, but we still have the 64bit equivalent which is green.