vcpkg deactivate does not unset environment variables

[Zitrax]

Describe the bug

In my registry I have this:

⋮

"windows,linux": {
  "message": "Updated environment variable MYVAR",
  "exports": {
    "paths": {
      "MYVAR": ""
    }
  }
}

⋮

Environment

• OS: WSL on Windows 11 which reports: Ubuntu 22.04.2 LTS
• vcpkg version: vcpkg package management program version 2023-12-12-1c9ec1978a6b0c2b39c9e9554a96e3e275f7556e

To Reproduce
Steps to reproduce the behavior:

1. vcpkg activate
2. echo $MYVAR
3. vcpkg deactivate
4. echo $MYVAR

Expected behavior

After deactivation MYVAR should no longer be set but it is.

Notice that I only see this on WSL, not under Windows. (I have not tested non-WSL linux)

Failure logs

If I run vcpkg deactivate --debug I see this on WSL:

debug: [00:00.160] --------[START SHELL SCRIPT FILE]--------
unset M
unset Z


--------[END SHELL SCRIPT FILE]---------

but on Windows I see:

debug: [00:00.116] --------[START SHELL SCRIPT FILE]--------
${ENV:MYVAR}=$null
${ENV:Z_VCPKG_UNDO}=$null


--------[END SHELL SCRIPT FILE]---------

So for some reason it tries to unset env variables with the first letter only.

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[Cheney-W]

Still present.

[Zitrax]

Thanks!