compctl --run: Make sure started computation has its own pgrp

compctl.c

@@ -105,6 +105,7 @@ run(int argc, char *argv[])
 	}
 	free(line);
 
+	setpgrp();
 	if (setpriority(PRIO_PROCESS, 0, COMPNICE) < 0)
 		perror("Warning: setpriority()");