os/exec: Cmd.{Run,Start} should fail if Cmd.Path is unset

[rolandshoemaker]

If Cmd.Path is unset, Cmd.Run and Cmd.Start should throw an error.

[gopherbot]

Change https://go.dev/cl/403759 mentions this issue: os/exec: return clear error for missing cmd.Path

[rolandshoemaker]

@gopherbot please open backport issues, this is a minor security issue.

[gopherbot]

Backport issue(s) opened: #53056 (for 1.17), #53057 (for 1.18).

Remember to create the cherry-pick CL(s) as soon as the patch is submitted to master, according to https://go.dev/wiki/MinorReleases.

[gopherbot]

Change https://go.dev/cl/408577 mentions this issue: [release-branch.go1.18] os/exec: return clear error for missing cmd.Path

[gopherbot]

Change https://go.dev/cl/408578 mentions this issue: [release-branch.go1.17] os/exec: return clear error for missing cmd.Path