cmMessenger: Revert to non-color messages on Windows

Since commit 0a0a0f8a (cmMessenger: Color messages to terminal by
type, 2021-05-18, v3.21.0-rc1~146^2) the message output no longer goes
through our custom streambuf on Windows that converts output encoding.
This can cause messages to be printed with the wrong encoding in a
Windows Console.  It also causes messages to have a mix of LF and CRLF
newlines because `stderr` converts LF to CRLF but our custom streambuf
does not.

Revert to using just `cerr` for messages on Windows.  Another approach
will be needed to achieve color output on Windows later.

Fixes: #22444

Source/cmakemain.cxx

@@ -153,9 +153,20 @@ std::string cmakemainGetStack(cmake* cm)
 void cmakemainMessageCallback(const std::string& m,
                               const cmMessageMetadata& md, cmake* cm)
 {
+#if defined(_WIN32)
+  // FIXME: On Windows we replace cerr's streambuf with a custom
+  // implementation that converts our internal UTF-8 encoding to the
+  // console's encoding.  It also does *not* replace LF with CRLF.
+  // Since stderr does not convert encoding and does convert LF, we
+  // cannot use it to print messages.  Another implementation will
+  // be needed to print colored messages on Windows.
+  static_cast<void>(md);
+  std::cerr << m << cmakemainGetStack(cm) << "\n";
+#else
   cmsysTerminal_cfprintf(md.desiredColor, stderr, "%s", m.c_str());
   fflush(stderr); // stderr is buffered in some cases.
   std::cerr << cmakemainGetStack(cm) << "\n";
+#endif
 }
 
 void cmakemainProgressCallback(const std::string& m, float prog, cmake* cm)

Tests/RunCMake/message/RunCMakeTest.cmake

 include(RunCMake)
 
+run_cmake_script(newline)
+
 run_cmake(defaultmessage)
 run_cmake(nomessage)
 run_cmake(message-internal-warning)

Tests/RunCMake/message/newline-script.cmake

+message(STATUS "one\ntwo")
+message("one\ntwo")

Tests/RunCMake/message/newline-stdout.txt

+-- out='2d2d206f6e650a74776f0a'
+-- err='6f6e650a74776f0a'

Tests/RunCMake/message/newline.cmake

+execute_process(
+  COMMAND "${CMAKE_COMMAND}" -P "${CMAKE_CURRENT_LIST_DIR}/newline-script.cmake"
+  OUTPUT_FILE newline-script-stdout.txt
+  ERROR_FILE newline-script-stderr.txt
+  )
+foreach(f out err)
+  file(READ newline-script-std${f}.txt hex HEX)
+  message(STATUS "${f}='${hex}'")
+endforeach()