Check `system-type` in `asm-interp`

[dvanhorn]

Similar to how we check for nasm and provide a helpful error message, we should check that (system-type 'arch) gives you 'x86_64 and if not say that you've installed the wrong version of Racket and need to install the Intel 64-bit version.

[pdarragh]

I wonder if we should also provide some test that can be run after installation that explicitly checks the tool chain and gives explicit feedback about each step?