config/scripts/switch-arch: Enable building from aarch64, riscv64.

[Millak]

aarch64 and riscv64 are 64-bit CPUs, and without configuring the longbits as 64 writing the dictionary core file would fail with a segfault.

[mcayland]

Thanks for the patch! Whilst the repositories are hosted on github, the project still makes use of mailing lists for patches/code review. If you can resend the patch to the OpenBIOS mailing list (https://mail.coreboot.org/postorius/lists/openbios.openbios.org/) we should be able to get this reviewed/applied fairly quickly.