Revert this commit for libstdc++-prettyprinters (only cxx17, 91997
doesn't exist in this tree) since gcc8 does not default to c++17.  The
context has been adapted but the change should be exact:

commit 0498d2d09a2364aae1e6b5e085c8ebb8fc517684
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Mon May 10 16:22:54 2021 +0100

    libstdc++: Remove redundant -std=gnu++17 option from remaining tests

Also remove the filesystem tests since it's not supported by RHEL8 gcc.

diff --git b/libstdc++-v3/testsuite/libstdc++-prettyprinters/cxx17.cc a/libstdc++-v3/testsuite/libstdc++-prettyprinters/cxx17.cc
index 72c66d3b785..98e21e963fe 100644
--- b/libstdc++-v3/testsuite/libstdc++-prettyprinters/cxx17.cc
+++ a/libstdc++-v3/testsuite/libstdc++-prettyprinters/cxx17.cc
@@ -1,4 +1,4 @@
-// { dg-options "-g -O0" }
+// { dg-options "-g -O0 -std=gnu++17" }
 // { dg-do run { target c++17 } }
 
 // Copyright (C) 2014-2024 Free Software Foundation, Inc.
@@ -18,7 +18,6 @@
 // with this library; see the file COPYING3.  If not see
 // <http://www.gnu.org/licenses/>.
 
-#include <filesystem>
 #include <any>
 #include <optional>
 #include <variant>
@@ -120,13 +119,6 @@ main()
 // { dg-final { regexp-test q {std::shared_ptr.int \[2\]. \(use count 2, weak count 1\) = {get\(\) = 0x.*}} } }
 // { dg-final { regexp-test wq {std::weak_ptr.int \[2\]. \(use count 2, weak count 1\) = {get\(\) = 0x.*}} } }
 
-  std::filesystem::path path0;
-// { dg-final { note-test path0 {filesystem::path ""} } }
-  std::filesystem::path path1("filename");
-// { dg-final { note-test path1 {filesystem::path "filename"} } }
-  std::filesystem::path path2("/dir/.");
-// { dg-final { note-test path2 {filesystem::path "/dir/." = {[root-directory] = "/", [1] = "dir", [2] = "."}} } }
-
   std::cout << "\n";
   return 0;			// Mark SPOT
 }