internal/gocommand: add openbsd to the set of GOOS to debug

We encountered a hanging go command on openbsd, which unfortunately did
not have logic to SIGQUIT. Add openbsd to the special set of GOOS in
handleHandingGoCommand.

Updates golang/go#54461

Change-Id: I36e32559f23a3ace28a1088a1f910642eb0074ec
Reviewed-on: https://go-review.googlesource.com/c/tools/+/644016
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Alan Donovan <[email protected]>
Auto-Submit: Robert Findley <[email protected]>

Author: findleyr

internal/gocommand/invoke.go

@@ -426,7 +426,7 @@ func runCmdContext(ctx context.Context, cmd *exec.Cmd) (err error) {
 // cause of a hanging Go command, and then exits with log.Fatalf.
 func handleHangingGoCommand(start time.Time, cmd *exec.Cmd, resChan chan error) {
 	switch runtime.GOOS {
-	case "linux", "darwin", "freebsd", "netbsd":
+	case "linux", "darwin", "freebsd", "netbsd", "openbsd":
 		fmt.Fprintln(os.Stderr, `DETECTED A HANGING GO COMMAND
 
 			The gopls test runner has detected a hanging go command. In order to debug