How do I force Waf to build only for "-arch i386" target on OSX and not "-arch x86_64 -arch i386"?

Question

Waf is adding "-arch x86_64 -arch i386" and trying to create universal binaries.

Linking is failing because I only have 32 bit runtimes and Waf is trying to create a universal binary. How do I get Waf to remove "-arch x86_64 -arch i386" flags and only compile for "-arch i386"?