ls: fix SEGV when --color is used and ENABLE_LS_COLOR=n

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/coreutils/ls.c b/coreutils/ls.c
index b2adb0c..e5375a6 100644
--- a/coreutils/ls.c
+++ b/coreutils/ls.c
@@ -1086,7 +1086,7 @@
 	static const char ls_longopts[] ALIGN1 =
 		"full-time\0" No_argument "\xff"
 		"group-directories-first\0" No_argument "\xfe"
-		"color\0" Optional_argument "\xfd"
+		IF_FEATURE_LS_COLOR("color\0" Optional_argument "\xfd")
 	;
 #endif