There's no way to specify the environment variables for an installer exe

[coolreader18]

Description of the new feature/enhancement

I'm working on a rustup manifest, but the rustup binary is a chimera, so if it's named rustup-init then it will run the installer, or if it's named rustc it'll look for a rustc executable, but winget downloads it as rust.rustup.1.21.1.exe, which doesn't work. There's a few ways to theoretically solve this. a, I could set the Id field to rustup-init.*, which wouldn't be ideal as it goes against the conventions in the manifest spec. b, there could be some way to specify the file name of the downloaded installer. or c, there could be some way to pass environment variables (specifically RUSTUP_FORCE_ARG0 in this case) to the installer, which I think would be the most common use case for package manifests.

I'm not sure exactly the best way to do this, but perhaps it could be an extension to the Switches option? Perhaps Switches.Log: $env:LOG_OPTIONS=logfile=<LOGPATH> could set the LOG_OPTIONS env var to logfile=<LOGPATH>, where <LOGPATH> would be substituted for the log path as it is usually.

Although, to get rust/rustup working, a FileName: option would be the easiest to define in the spec.