switch_root: improve behavior on error; improve help text
*: make "can't execute '%s'" message uniform

diff --git a/shell/cttyhack.c b/shell/cttyhack.c
index 0aa4b8a..572a3af 100644
--- a/shell/cttyhack.c
+++ b/shell/cttyhack.c
@@ -73,5 +73,5 @@
 	}
 
 	BB_EXECVP(argv[0], argv);
-	bb_perror_msg_and_die("cannot exec '%s'", argv[0]);
+	bb_perror_msg_and_die("can't execute '%s'", argv[0]);
 }