Added x86_64 (Simulator) architecture to build.

Jeff,

Thanks for your scripts and SO answers. I have added the x86_64 architecture and it appears to work in the build so far, although I haven't run tests with the result, so please double check. I'm going to try to use your env scripts to help me with an all iOS architecture fips canister and fips capable library build. If it works I may have more contributions, perhaps to a new library...