ash: fix infinite loop on exit if tty is not there anymore

shell/README

@@ -1,5 +1,10 @@
 Various bits of what is known about busybox shells, in no particular order.
 
+2007-04-28
+hush: Ctrl-C and Ctrl-Z for single NOFORK commands are working.
+Memory and other resource leaks (opendir) are not addressed
+(testcase is "rm -i" interrupted by ctrl-c).
+
 2007-04-21
 hush: "sleep 5 | sleep 6" + Ctrl-Z + fg seems to work.
 "rm -i" + Ctrl-C, "sleep 5" + Ctrl-Z still doesn't work

shell/ash.c

@@ -3501,7 +3501,9 @@ setjobctl(int on)
 		/* turning job control off */
 		fd = ttyfd;
 		pgrp = initialpgrp;
-		xtcsetpgrp(fd, pgrp);
+		/* was xtcsetpgrp, but this can make exiting ash
+		 * with pty already deleted loop forever */
+		tcsetpgrp(fd, pgrp);
 		setpgid(0, pgrp);
 		setsignal(SIGTSTP);
 		setsignal(SIGTTOU);