Fix "tailscale ssh" when built with ts_include_cli tag

Signed-off-by: Sandro Jäckel <sandro.jaeckel@gmail.com>

cmd/tailscale/cli/ssh.go

@@ -84,10 +84,6 @@ func runSSH(ctx context.Context, args []string) error {
 		// of failing. But for now:
 		return fmt.Errorf("no system 'ssh' command found: %w", err)
 	}
-	tailscaleBin, err := os.Executable()
-	if err != nil {
-		return err
-	}
 	knownHostsFile, err := writeKnownHosts(st)
 	if err != nil {
 		return err
@@ -115,8 +111,7 @@ func runSSH(ctx context.Context, args []string) error {
 		}
 
 		argv = append(argv,
-			"-o", fmt.Sprintf("ProxyCommand %q %s nc %%h %%p",
-				tailscaleBin,
+			"-o", fmt.Sprintf("ProxyCommand tailscale %s nc %%h %%p",
 				socketArg,
 			))
 	}