since Vite 3.0.0-alpha.5 with 2.0.0 -alpha.1 legacy plugin is producing code incompatible with ie 11

[kalvenschraut]

Describe the bug

In polyfills-legacy arrow functions are being used which are not valid syntax for IE 11.

Reproduction

https://github.com/RtVision/vite-alpha-legacy-repro

System Info

System:
    OS: Linux 5.15 Gentoo/Linux
    CPU: (4) x64 Intel(R) Core(TM) i5-6500 CPU @ 3.20GHz
    Memory: 19.03 GB / 26.78 GB
    Container: Yes
    Shell: 5.1.16 - /bin/bash
  Binaries:
    Node: 16.13.1 - /usr/bin/node
    Yarn: 1.22.18 - ~/.local/share/pnpm/yarn
    npm: 8.6.0 - /usr/bin/npm
    Watchman: 2022.03.21.00 - /usr/bin/watchman
  Browsers:
    Firefox: 91.7.0esr
  npmPackages:
    @vitejs/plugin-legacy: ^2.0.0-alpha.1 => 2.0.0-alpha.1
    vite: ^3.0.0-alpha.12 => 3.0.0-alpha.12

Used Package Manager

pnpm

Logs

No response

Validations

• Follow our Code of Conduct
• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.
• Make sure this is a Vite issue and not a framework-specific issue. For example, if it's a Vue SFC related bug, it should likely be reported to https://github.com/vuejs/core instead.
• Check that this is a concrete bug. For Q&A open a GitHub Discussion or join our Discord Chat Server.
• The provided reproduction is a minimal reproducible example of the bug.

[sapphi-red]

It happens with plugin-legacy 1.8.2 and vite 3.0.0-alpha.5.
But it does not happen with plugin-legacy 1.8.2 and vite 3.0.0-alpha.4.