install: run command now kills child process on SIGTERM to cleanly exit (bp #4896)

[mergify]

This is an automated backport of pull request #4896 done by Mergify.io

Cherry-pick of 2abe051 has failed:

On branch mergify/bp/v0.16/pr-4896
Your branch is up to date with 'origin/v0.16'.

You are currently cherry-picking commit 2abe051a1.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:

	modified:   install/src/command.rs

Unmerged paths:
  (use "git add <file>..." to mark resolution)

	both modified:   Cargo.lock
	both modified:   install/Cargo.toml

To fixup this pull request, you can check out it locally. See documentation: https://help.github.com/articles/checking-out-pull-requests-locally/

[solana-grimes]

💔 Unable to automerge due to CI failure

[mvines]

#4899