http://www.bugless.co.uk/howto/qt3-ub.html より
Firstly strip the symbol tables from the 2 executables using the "strip" utility:
strip myapp-intel strip myapp-ppc
Next use "lipo" to stitch the 2 executables together into a single Universal Binary:
lipo -create myapp-intel myapp-ppc -output myapp
Once this has finished run the following to check the new executable:
file myapp
This should output something like the following:
myapp: Mach-O universal binary with 2 architectures myapp (for architecture i386): Mach-O executable i386 myapp (for architecture ppc): Mach-O executable ppc
And finally copy the executable back into your myapp.app tree under Contents/MacOS.
