Enable building a gold version for mac.

b.sh

@@ -69,6 +69,9 @@ do
 		--sanitize) echo "Enabling address-sanitizer if available"
 			CMAKE_ARGS="-DUSE_ASAN=ON ${CMAKE_ARGS}"
 			;;
+		--gold) echo "Gold build enabled"
+			CMAKE_ARGS="-DGOLD=ON ${CMAKE_ARGS}"
+			;;
 		*) MAKE_OPT="$1 ${MAKE_OPT}"
 			;;
 	esac