install: fix help text

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/coreutils/install.c b/coreutils/install.c
index 6e19994..73f9c70 100644
--- a/coreutils/install.c
+++ b/coreutils/install.c
@@ -8,7 +8,7 @@
 
 /* -v, -b, -c are ignored */
 //usage:#define install_trivial_usage
-//usage:	"[-cdDsp] [-o USER] [-g GRP] [-m MODE] [-d DIR] [SOURCE]... DEST"
+//usage:	"[-cdDsp] [-o USER] [-g GRP] [-m MODE] [-t DIR] [SOURCE]... DEST"
 //usage:#define install_full_usage "\n\n"
 //usage:       "Copy files and set attributes\n"
 //usage:     "\n	-c	Just copy (default)"