[ORC-RT] Configure the ORC runtime for more architectures and platforms

Enable building the ORC runtime for 64-bit and 32-bit ARM architectures,
and for all Darwin embedded platforms (iOS, tvOS, and watchOS). This
covers building the cross-platform code, but does not add TLV runtime
support for the new architectures, which can be added independently.

Incidentally, stop building the Mach-O TLS support file unnecessarily on
other platforms.

Differential Revision: https://reviews.llvm.org/D112111