Complete prebuild setup

[LandryNorris]

Currently, on this branch, I have prebuilding working for LinuxX64, LinuxArm64, and DarwinX64.

Todos:

• Cross-compile to DarwinArm64 (it seems to be different from LimuxArm64 cross-compiling)
• Cross-compile from Linux to Windows (mingw is not fully compatible, so a separate node.lib file needs to be built using node.def).

Until these issues are fixed, we'll drop prebuilts.

[LandryNorris]

This will likely rrequire changes to librhsp (the C library). Any changes should be upstreamed, and if this branch is merged, changes need to be rebased out. Alternatively, when the code is finalized, a new branch can be created and changes brought out to that.