Can't use fs with relative paths in svelte.config.js since the postinstall lifecycle hook has a different $PWD

[ghost]

Describe the bug

The most recent update of SvelteKit can not be installed on my project because of my use of fs.readFileSync and relative paths inside of svelte.config.js.
It seems like the added lifecycle hook executes the code of svelte.config.js inside of node_modules/@sveltejs/kit (according to process.cwd()), which of course breaks any relative paths and finally makes fs.readFileSync throw, which in turn makes npm update or npm install fail and not change anything.
I use a JSON file to populate the content of config.kit.prerender.entries, so accessing a file using Nodes fs is crucial.

Reproduction

🎩 Repository for reproduction
I quickly made a skeleton project using npm create svelte@latest and added the following four lines to the top of svelte.config.js:
https://github.com/martinszar/sveltekit-lifecycle-pwd-reproduction/blob/main/svelte.config.js#L1-L4

To observe the bug just clone the repo and run npm install. I additionally added a console.log marked with the 🚨 emoji, which will log process.cwd().

Logs

No response

System Info

System:
    OS: Linux 5.18 Fedora Linux 36 (Workstation Edition)
    CPU: (4) x64 Intel(R) Core(TM) i5-7500 CPU @ 3.40GHz
    Memory: 10.09 GB / 15.49 GB
    Container: Yes
    Shell: 3.5.0 - /usr/bin/fish
  Binaries:
    Node: 16.14.0 - /usr/bin/node
    npm: 8.13.1 - /usr/local/bin/npm
  Browsers:
    Firefox: 102.0

Severity

blocking an upgrade

Additional Information

No response

[Conduitry]

Here

kit/packages/kit/src/cli.js

Line 58 in ef6d42b

const cwd = event === 'postinstall' ? process.env.INIT_CWD ?? '' : process.cwd();

we've got some logic for looking for the svelte.config.js file in a different place depending on whether we're in a postinstall event or not. Presumably we could process.chdir() here rather than simply loading the config file from the appropriate directory.

[Conduitry]

That doesn't appear to quite work. I'm guessing the CWD needs to be changed back afterwards.
edit: Maybe I was just running into something weird with linking packages?

Also, for the record, you repro is trying to load "./.svelte.config.js" rather than "./svelte.config.js".

[Conduitry]

Looks like the fix worked. Should be good now with next.401.