Passing an array as sass / scss importer does not work properly.

[j000]

In config, passing importer as an array does nothing:
css: { preprocessorOptions: { sass: { importer: [SomeFunction, OtherFunction] } } }
Passing single function works as intended.

#3395 introduced this part of code:
https://github.com/axe-me/vite/blob/465ee5a453579517fa7887f1c9c2b66614270bdc/packages/vite/src/node/plugins/css.ts#L932-L936

Array.concat does not modify source array but returns a modified one. Here it's not assigned to anything.

BTW Thank you, for a nice and useful piece of software :)

System Info

Output of npx envinfo --system --npmPackages vite,@vitejs/plugin-vue --binaries --browsers:

  System:
    OS: Linux 5.12 Gentoo/Linux
    CPU: (8) x64 AMD Ryzen 5 2400G with Radeon Vega Graphics
    Memory: 260.44 MB / 7.56 GB
    Container: Yes
    Shell: 5.8 - /bin/zsh
  Binaries:
    Node: 16.2.0 - /usr/bin/node
    Yarn: 1.22.10 - /usr/bin/yarn
    npm: 7.13.0 - /usr/bin/npm
  Browsers:
    Firefox: 88.0.1
  npmPackages:
    @vitejs/plugin-vue: ^1 => 1.2.2 
    vite: ^2 => 2.3.3 

Used package manager: yarn

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[patak-dev]

@j000 would you like to send a PR to fix this?