Running applications against a different SDK in OS X?

Question

Summary

I want to run my cross-compiled application against the 10.5 libraries. Is there an environmental variable that allows this to work?

Longer version

I cross-compiled my OS X C++ application for a 10.5 target, on a 10.6 host. It compiles fine. The compiled application is linked against libraries like /usr/lib/libstdc++.6.dylib. When I run it on my system, it will use the 'host' version of libraries, which are 10.6. I'd like to test it against the 10.5 versions, which are all contained in the `/Developer/SDKs/MacOSX10.5.sdk directory. How do I do this?

I tried various flavours of DYLD_LIBRARY_PATH, DYLD_ROOT_PATH, etc, as documented in the manual, but I haven't managed to get it working.