@cloudflare/wrangler postinstall script does not exit


I have to force exit, and the binary is not linked.

And I modified the script
```js
#!/usr/bin/env node

const why = require('why-is-node-running')
const { install } = require("./binary");

install().then(() => {
setInterval(() => {
console.log('-------');
why()
}, 1000)
})
```

And logs as
```txt
$ node ./install-wrangler.js
Downloading release https://workers.cloudflare.com/get-npm-wrangler-binary/1.7.0/x86_64-apple-darwin
wrangler has been installed!
-------
There are 10 handle(s) keeping the process running

# TTYWRAP
/Users/magicdawn/.npm-global/lib/node_modules/@cloudflare/wrangler/node_modules/debug/src/node.js:76 - : tty.isatty(process.stderr.fd);
/Users/magicdawn/.npm-global/lib/node_modules/@cloudflare/wrangler/node_modules/debug/src/debug.js:120 - debug.useColors = exports.useColors();
/Users/magicdawn/.npm-global/lib/node_modules/@cloudflare/wrangler/node_modules/follow-redirects/index.js:6 - var debug = require("debug")("follow-redirects");

# SIGNALWRAP
/Users/magicdawn/.npm-global/lib/node_modules/@cloudflare/wrangler/node_modules/debug/src/node.js:76 - : tty.isatty(process.stderr.fd);
/Users/magicdawn/.npm-global/lib/node_modules/@cloudflare/wrangler/node_modules/debug/src/debug.js:120 - debug.useColors = exports.useColors();
/Users/magicdawn/.npm-global/lib/node_modules/@cloudflare/wrangler/node_modules/follow-redirects/index.js:6 - var debug = require("debug")("follow-redirects");

# TTYWRAP
/Users/magicdawn/.npm-global/lib/node_modules/@cloudflare/wrangler/node_modules/binary-install/src/binary.js:88 - console.log("Downloading release", this.url);
/Users/magicdawn/.npm-global/lib/node_modules/@cloudflare/wrangler/binary.js:37 - return binary.install();

# TCPWRAP
(unknown stack trace)

# TLSWRAP
(unknown stack trace)

# DNSCHANNEL
(unknown stack trace)

# HTTPCLIENTREQUEST
(unknown stack trace)

# Timeout
/Users/magicdawn/.npm-global/lib/node_modules/@cloudflare/wrangler/install-wrangler.js:7 - setInterval(() => {

# ZLIB
/Users/magicdawn/.npm-global/lib/node_modules/@cloudflare/wrangler/node_modules/minizlib/index.js:60 - this[_handle] = new realZlib[mode](opts)
/Users/magicdawn/.npm-global/lib/node_modules/@cloudflare/wrangler/node_modules/minizlib/index.js:193 - super(opts, mode)
/Users/magicdawn/.npm-global/lib/node_modules/@cloudflare/wrangler/node_modules/minizlib/index.js:292 - super(opts, 'Unzip')
/Users/magicdawn/.npm-global/lib/node_modules/@cloudflare/wrangler/node_modules/tar/lib/parse.js:347 - this[UNZIP] = new zlib.Unzip()

# TickObject
(unknown stack trace)
```

install-wrangler.js と binary.js から始め、次にレポートに記載された npm のインストールを再現します。postinstall プロセスがアクティブなままになる理由と、binary がリンクされない理由を確認します。インストールが強制終了を必要とせずに完了し、binary がリンクされれば完了です。

索引モデルが issue の本文から書いたものです。