under Leopard, and got this far
bash-3.2$ sudo ./configure
Password:
checking for path to top of build tree... dyld: unknown required load command 0x80000022
configure: error: cannot determine current directory
I'd expect that on Leopard. Unless someone does a Leopard-specific build, I suspect you're out of luck.
I don't really know what this means. I'm kind of expecting that I have
Apple adds new stuff to its dynamic loader in every OS release, and the result usually isn't compatible with earlier releases by default, in my experience (that'd be from Tiger through Lion at this point). You need to specify an ABI compatibility level to build stuff that will run on older releases, including just being understood by dyld.
Part of the problem here is that a default Xcode 4.x install only includes the 10.6 and 10.7 SDKs. I'm not seeing any way to customize the install, so it looks like Xcode 4 cannot be used to build for Leopard; someone will have to do the Leopard-compatible build on Leopard or on Snow Leopard with Xcode 3.6.