A fork from the gdb tarball(s) from opensource.apple.com
Try the top-level ./configure script.
Or just try using make with the top-level Makefile, as it is not actually generated by the top-level ./configure script (it just sits there independently of it).
Or try using ant.
Or try (what I once thought was) the darwinbuild plist.
Or try using the Xcode project in src/gdb/macosx or something.
Or if you know what the heck this tool is that Apple refers to as "buildit" in their Makefile commentary, you can try using that.
Most of these do not actually work, but it is always worth a shot.