The attached script will build gpg v1.4.9 on OS X as a universal binary compatible with 10.4+. I'd stuff it into your installer source, but the SVN seems way out of date. (It doesn't work with the PackageMaker either).
In order to run this script, you simply need to set the BUILD_PATH at the top.
I can run this without incident on Intel 32-bit, 10.5.5. If it helps any, my build log is also attached.
Let me know if you have questions.
Log of my build execution.
File Added: build.sh
The build script.