Config paths.base and static folder don't play well together

[DblK]

Describe the bug

When adding a path.base all the path marked with %svelte.assets% are replaced with the path as expected.
This works great with npm run build.
However during dev mode, the static folder still represent / instead of the value of path.base.

Reproduction

Add the following configuration:

kit: {
  ...,
  paths: {
    base: '/admin',
  },
}

And add <link rel="stylesheet" href="%svelte.assets%/myCSS.css" /> in app.html.
In your static folder have the following structure:

| static
  |- myCss.css

The css in dev mode won't work unless you manually create the same folder

| static
  |- admin
    |- myCss.css

I wish to stick the file myCss.css at the root of static folder and let the magic happens to serve those file as if under paths.base (in my example /admin/myCSS.css stored in static/myCSS.css

Logs

No response

System Info

System:
    OS: macOS 10.15.7
    CPU: (8) x64 Intel(R) Core(TM) i7-4870HQ CPU @ 2.50GHz
    Memory: 128.55 MB / 16.00 GB
    Shell: 5.7.1 - /bin/zsh
  Binaries:
    Node: 14.17.0 - ~/.nvm/versions/node/v14.17.0/bin/node
    npm: 7.24.0 - ~/.nvm/versions/node/v14.17.0/bin/npm
  Browsers:
    Chrome: 97.0.4692.71
    Firefox: 89.0.2
    Safari: 14.0.3
  npmPackages:
    @sveltejs/adapter-auto: next => 1.0.0-next.9 
    @sveltejs/adapter-static: ^1.0.0-next.24 => 1.0.0-next.24 
    @sveltejs/kit: ^1.0.0-next.218 => 1.0.0-next.218 
    svelte: ^3.45.0 => 3.45.0

Severity

serious, but I can work around it

Additional Information

I add the path in my config for building but removing during dev. This is pretty annoying.

[DblK]

After search seems to be close to #3232

[ebeloded]

I just came here to report this exact issue, but you already did it 👍

Issue #3232 description focuses on the static adapter, but the problem is the same for the node-adapter. Static assets location should respect paths.base.

[benmccann]

I think this should be fixed by #3346