[libcxx] Fix the function name in exceptions from create_directories

[mstorsjo]

Summary

If the nested create_directory call fails, we'd still want to
re-report the errors with the create_directories function name,
which is what the caller called.

This fixes one aspect from MS STL's tests for std::filesystem.

[mstorsjo]

Rerun CI

[curdeius]

LGTM.

libcxx/src/filesystem/operations.cpp

if (not exists(parent_st)) {
         return err.report(errc::invalid_argument);
       __create_directories(parent, ec);
       if (ec && *ec) {
         return false;
       }
     } else if (not is_directory(parent_st))
       return err.report(errc::not_a_directory);
   }
-  return __create_directory(p, ec);
+  bool ret = __create_directory(p, &m_ec);
+  if (m_ec)
+    return err.report(m_ec);
+  return ret;
 }
 
 bool __create_directory(const path& p, error_code* ec) {
   ErrorHandler<bool> err("create_directory", ec, &p);
 
   if (detail::mkdir(p.c_str(), static_cast<int>(perms::all)) == 0)
     return true;
 

libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.create_directories/create_directories.pass.cpp

TEST_CASE(dest_final_part_is_file)
     std::error_code ec = GetTestEC();
     TEST_CHECK(fs::create_directories(dir, ec) == false);
     TEST_CHECK(ec);
     TEST_CHECK(ErrorIs(ec, std::errc::not_a_directory));
     TEST_CHECK(is_regular_file(file));
     TEST_CHECK(!exists(dir));
 }
 
+TEST_CASE(dest_is_empty_path)
+{
+    std::error_code ec = GetTestEC();
+    TEST_CHECK(fs::create_directories(fs::path{}, ec) == false);
+    TEST_CHECK(ec);
+    TEST_CHECK(ErrorIs(ec, std::errc::no_such_file_or_directory));
+    ExceptionChecker Checker(path{}, std::errc::no_such_file_or_directory,
+                             "create_directories");
+    TEST_CHECK_THROW_RESULT(filesystem_error, Checker,
+                            fs::create_directories(path{}));
+}
+
 #ifdef _WIN32
 TEST_CASE(nonexistent_root)
 {
     std::error_code ec = GetTestEC();
     // If Q:\ doesn't exist, create_directories would try to recurse upwards
     // to parent_path() until it finds a directory that does exist. As the
     // whole path is the root name, parent_path() returns itself, and it
     // would recurse indefinitely, unless the recursion is broken.
     if (!exists("Q:\\"))
        TEST_CHECK(fs::create_directories("Q:\\", ec) == false);
     TEST_CHECK(fs::create_directories("\\\\nonexistentserver", ec) == false);
 }
 #endif
 
 TEST_SUITE_END()