UNSTABLE: New API, yet to be vetted.
Clear environmental variables from parent process.
Doesn't guarantee that only
opt.env variables are present,
as the OS may set environmental variables for processes.
The working directory of the process. If not specified, the cwd of the parent process is used.
An AbortSignal that allows closing the process using the corresponding AbortController by sending the process a SIGTERM signal. Not supported in spawnSync.