https://bugs.gentoo.org/335347

fix building with older linux headers that don't define SO_MARK

--- ping_common.c
+++ ping_common.c
@@ -485,6 +485,7 @@
 			fprintf(stderr, "Warning: no SO_TIMESTAMP support, falling back to SIOCGSTAMP\n");
 	}
 #endif
+#ifdef SO_MARK
 	if (options & F_MARK) {
 		if (setsockopt(icmp_sock, SOL_SOCKET, SO_MARK,
 				&mark, sizeof(mark)) == -1) {
@@ -494,6 +495,7 @@
 			fprintf(stderr, "Warning: Failed to set mark %d\n", mark);
 		}
 	}
+#endif
 
 	/* Set some SNDTIMEO to prevent blocking forever
 	 * on sends, when device is too slow or stalls. Just put limit