🛠 Fix assumptions of Unicode for Clang-on-Windows

— 💡 MSVC fixed this linker errors (at some point); should check for newer versions and just use the char32_t-based version properly.

include/fmt/chrono.h

@@ -362,7 +362,7 @@ auto write_encoded_tm_str(OutputIt out, string_view in, const std::locale& loc)
   if (detail::is_utf8() && loc != get_classic_locale()) {
     // char16_t and char32_t codecvts are broken in MSVC (linkage errors) and
     // gcc-4.
-#if FMT_MSC_VERSION != 0 || \
+#if FMT_MSC_VERSION < 1932 || \
     (defined(__GLIBCXX__) && !defined(_GLIBCXX_USE_DUAL_ABI))
     // The _GLIBCXX_USE_DUAL_ABI macro is always defined in libstdc++ from gcc-5
     // and newer.

include/fmt/core.h

@@ -233,7 +233,13 @@
 #endif
 
 #ifndef FMT_UNICODE
-#  define FMT_UNICODE !FMT_MSC_VERSION
+#  if FMT_CLANG_VERSION
+#    define FMT_UNICODE 1
+#  elif defined(_MSVC_EXECUTION_CHARACTER_SET) && (_MSVC_EXECUTION_CHARACTER_SET == 65001)
+#    define FMT_UNICODE 1
+#  else
+#    define FMT_UNICODE !FMT_MSC_VERSION
+#  endif
 #endif
 
 #ifndef FMT_CONSTEVAL