[gcc r12-8611] libstdc++: check for openat with dirfd in std::filesystem

[Jonathan Wakely]

https://gcc.gnu.org/g:4eb15eceaac0bb900303986fc5164190d3692a0a

commit r12-8611-g4eb15eceaac0bb900303986fc5164190d3692a0a
Author: Alexandre Oliva <oliva@adacore.com>
Date:   Mon Jun 27 10:34:16 2022 -0300

    libstdc++: check for openat with dirfd in std::filesystem
    
    In the recent patch to check for openat, I missed an occurrence of
    dirfd in std::filesystem.
    
    for  libstdc++-v3/ChangeLog
    
            * src/c++17/fs_dir.cc (dir_and_pathname): Use dirfd if
            _GLIBCXX_HAVE_OPENAT.
    
    (cherry picked from commit 486893b1d325d22d54c1380937943913a7501f91)

Diff:
---
 libstdc++-v3/src/c++17/fs_dir.cc | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libstdc++-v3/src/c++17/fs_dir.cc b/libstdc++-v3/src/c++17/fs_dir.cc
index c67fe76bc14..25b33baa875 100644
--- a/libstdc++-v3/src/c++17/fs_dir.cc
+++ b/libstdc++-v3/src/c++17/fs_dir.cc
@@ -124,7 +124,7 @@ struct fs::_Dir : _Dir_base
   dir_and_pathname() const noexcept
   {
     const fs::path& p = entry.path();
-#if _GLIBCXX_HAVE_DIRFD
+#if _GLIBCXX_HAVE_DIRFD && _GLIBCXX_HAVE_OPENAT
     if (!p.empty())
       return {::dirfd(this->dirp), std::prev(p.end())->c_str()};
 #endif