Prepare bin_path logic for more platforms/architectures

[cknitt]

If we want to include binaries for additional platforms/architectures in the npm package (Linux arm64 would be the next candidate), we need to think about the bin path / directory name for those.

Currently we are supporting the following architectures:

• x64: darwin, linux, windows
• arm64: darwin

and we have some special logic in place to use "darwinarm64" for darwin on arm64.

To generalize while keeping compatible with the existing naming, we can use the following rule:

• For architecture x64, the directory name is just the platform name.
• For all other architectures, it is platform name + architecture name.

[cristianoc]

If it's backwards compatible it should be safe.