Add a test for std::filesystem API. NFC (#24721)

See #24722

Author: sbc100

test/other/test_std_filesystem.cpp

@@ -0,0 +1,19 @@
+#include <cstdint>
+#include <filesystem>
+#include <fstream>
+#include <iostream>
+
+namespace fs = std::filesystem;
+
+int main() {
+  fs::path tmp{std::filesystem::temp_directory_path()};
+
+  const auto foo{"foo"};
+  std::ofstream{tmp / foo} << foo; // creates file containing "foo"
+  std::cout << "remove(): " << fs::remove(tmp / foo) << '\n'; // success
+  std::cout << "remove(): " << fs::remove(tmp / foo) << '\n'; // fail
+
+  std::filesystem::create_directories(tmp / "abcdef/example");
+  const std::uintmax_t n{fs::remove_all(tmp / "abcdef")};
+  std::cout << "remove_all(): " << n << " files or directories\n";
+}

test/other/test_std_filesystem.out

@@ -0,0 +1,3 @@
+remove(): 1
+remove(): 0
+remove_all(): 2 files or directories

test/test_other.py

@@ -15035,6 +15035,10 @@ def test_fs_icase(self):
     # c++20 for ends_with().
     self.do_other_test('test_fs_icase.cpp', cflags=['-sCASE_INSENSITIVE_FS', '-std=c++20'])
 
+  @with_all_fs
+  def test_std_filesystem(self):
+    self.do_other_test('test_std_filesystem.cpp')
+
   def test_strict_js_closure(self):
     self.do_runf('hello_world.c', cflags=['-sSTRICT_JS', '-Werror=closure', '--closure=1', '-O3'])