Fix: alternate build targets

[Ayplow]

The old build scripts didn't use the given arguments to discover the binary's path, among other fixes.

• Update unit tests to properly test 'Unsupported environments'

[Ayplow]

There seems to be an issue causing arch to be undefined when npm explore node-sass -- npm run build is run, causing the binary to be written to the wrong folder. I can't begin to figure out why it's happening