Currently only the x86_64 target has a 64-bit environment in the form of gcc, binutils, etc. We should switch over to have this as the norm and only let the i386 target remain 32-bit.
The point of this is to speed up the builds as the 64-bit binaries are faster.
*** Bug 5520 has been marked as a duplicate of this bug. ***
We did part of this in bug 5308 when we removed support for 32-bit servers. The arch-independent server modules now mainly use x86_64 rather than i386 for their tooling.