[committed, 13 branch] libstdc++: Fix backported test [PR112490]

[Patrick Palka]

On the 13 branch and older, C++ >= 20 tests need an explicit dg-options
directive specifying the -std flag, otherwise they won't run by default.

	PR libstdc++/112490

libstdc++-v3/ChangeLog:

	* testsuite/24_iterators/const_iterator/112490.cc: Add
	dg-options directive.
---
 libstdc++-v3/testsuite/24_iterators/const_iterator/112490.cc | 1 +
 1 file changed, 1 insertion(+)

diff --git a/libstdc++-v3/testsuite/24_iterators/const_iterator/112490.cc b/libstdc++-v3/testsuite/24_iterators/const_iterator/112490.cc
index 9bb154847cff..e6e74eb675d4 100644
--- a/libstdc++-v3/testsuite/24_iterators/const_iterator/112490.cc
+++ b/libstdc++-v3/testsuite/24_iterators/const_iterator/112490.cc
@@ -1,3 +1,4 @@
+// { dg-options "-std=gnu++23" }
 // { dg-do compile { target c++23 } }
 
 // PR libstdc++/112490 - infinite meta error in
-- 
2.49.0.654.g845c48a16a