um: Missing pipe handling

UML does not handle sigpipe. As a result when running it under
expect or redirecting the IO from the console to an external program
it will crash if the program stops or exits.
Signed-off-by: NAnton Ivanov <antivano@cisco.com>
Signed-off-by: NRichard Weinberger <richard@nod.at>

arch/um/os-Linux/main.c

@@ -151,6 +151,7 @@ int __init main(int argc, char **argv, char **envp)
 #endif
 
 	do_uml_initcalls();
+	change_sig(SIGPIPE, 0);
 	ret = linux_main(argc, argv);
 
 	/*