> Is it a case of needing to use stock gcc rather than Apple's version, or
> certain versions of gcc, or something else...?

I use ./configure and make and it builds just fine.

OS X: 10.8.2; I have xcode 4.5.2 and its command-line-tools installed.

This is very odd.  I have the same setup and tried again with rc2.  The first time while dumping emacs I got the same error that I originally reported.  I did a make distclean and tried again.  Worked fine.

George