So far I've had the best success with defining the following before configure:
> export LDFLAGS="-Wl,-syslibroot,/Developer/SDKs/MacOSX10.4u.sdk -arch ppc -arch i386" > export CFLAGS="-isysroot /Developer/SDKs/MacOSX10.4u.sdk -arch i386 -arch ppc"
Sometimes this lead to:
gcc: -E, -S, -save-temps and -M options are not allowed with multiple -arch flags
in which case passing –disable-dependency-tracking to configure seemed to help.