fix: prefer module.isBuiltin when checking core modules

[patrickkfkan]

Currently, pkg uses module.builtinModules for checking core modules, while stripping any node: prefix. The problem is, certain core modules do not appear in builtinModules and can only be checked with module.isBuiltin. An example would be node:sqlite (note: this is a prefix-only module, which must be imported with the prefix intact). I came across this when trying to package my project that uses undici, which imports node:sqlite. Simplest way to illustrate this:

// example.js
const undici = require("undici");

Running:

pkg example.js

will throw:

> Error! Cannot read file, ENOENT
  node:sqlite
> Error! ENOENT: no such file or directory, open 'node:sqlite'

This PR fixes this by using module.isBuiltin if available.

[robertsLando]

Thanks for this! We were not able to to understand why this was happening

[TobiWo]

Thank you so much for bringing this up @patrickkfkan. This solved a big issue for me 🙏 .