Have you tried using lipo
?
lipo -remove ppc libwx_osx_cocoau-2.9.4.0.0.dylib -output libwx_osx_cocoau-2.9.4.0.0.dylib.intel
you can then see if everything still works with the new output lib (renaming back to the original name of course)
If that is accepted by the loader you could add this to your build script so that ppc is removed after it is build each time.