fix: Set source maps support via API

[varungandhi-src]

env on different systems behaves differently. On macOS,
env ABC XYZ will invoke ABC with argument XYZ.
On some Linux variants, you need env -S ABC XYZ for that.
On Alpine, the -S flag is not supported, and there is seemingly
no way of passing arguments.

So this patch undoes the accidental breakage in #179
and uses the getSourceMapsSupport API.

Technically, both process.setSourceMapsEnabled and
module.setSourceMapsSupport are experimental functions,
so to be safe, we do a dynamic existence check before calling
them for portability across Node versions.