Add in the “-arch” flag for osx gpp compilers

The OSX gcc compiler needs to have an `-arch XXX` flag passed to it or else it creates binaries for the current system.  This prevents you from specifying, for example `-Dnar.arch=i386` and actually getting i386 binaries from the compiler.

This patch adds the appropriate `-arch XXX` flags to the options in the default aol.properties.