export concat view in modules

Author: changkhothuychung

libcxx/modules/std/ranges.inc

@@ -176,6 +176,15 @@ export namespace std {
     } // namespace views
 #endif // _LIBCPP_STD_VER >= 23
 
+#if _LIBCPP_STD_VER >= 26
+    // [range.concat.view], concat_view
+    using std::ranges::concat_view;
+
+    namespace views {
+      using std::ranges::views::concat;
+    } // namespace views
+#endif // _LIBCPP_STD_VER >= 26
+
     // [range.filter], filter view
     using std::ranges::filter_view;