On BSD platforms, there is a clear seperation between the OS and third
party packages. Here, bash is a third party package so it won't be
installed to /bin.
FreeBSD: /usr/local/bin/bash
NetBSD: /usr/pkg/bin/bash
OpenBSD: /usr/ports/bin/bash
As such, we need to use /usr/bin/env to launch these scripts.
Credit: @rsmarples
PR-URL: https://github.com/npm/cli/pull/212
Close: #212
Reviewed-by: @isaacs
