[PATCH] libstdc++: Export std::byteswap from std.cc.in [PR121373]

[hexne]

std::byteswap was added to the <bit> header file in c++23 and has been
implemented, but it was not exported in std.cc.in. Therefore, when
using import std, std::byteswap cannot be used. Exporting it in
std.cc.in can solve this problem.

Tested on x86_64-linux.
Signed-off-by: hexne <print...@gmail.com>
diff --git a/libstdc++-v3/src/c++23/std.cc.in b/libstdc++-v3/src/c++23/std.cc.in
index 9301ed90c00..61f0b715b36 100644
--- a/libstdc++-v3/src/c++23/std.cc.in
+++ b/libstdc++-v3/src/c++23/std.cc.in
@@ -663,6 +663,7 @@ export namespace std
   using std::bit_ceil;
   using std::bit_floor;
   using std::bit_width;
+  using std::byteswap;
   using std::countl_one;
   using std::countl_zero;
   using std::countr_one;