[libc++] Fix check for _LIBCPP_HAS_NO_WIDE_CHARACTERS in features.py (llvm#131675)

The patch that added the new locale Lit features was created before we
switched to a 0-1 macro for _LIBCPP_HAS_WIDE_CHARACTERS, leading to that
patch referring to the obsolete _LIBCPP_HAS_NO_WIDE_CHARACTERS macro
that is never defined nowadays.

(cherry picked from commit 297f6d9)

Author: ldionne

libcxx/utils/libcxx/test/features.py

@@ -440,7 +440,8 @@ def _mingwSupportsModules(cfg):
                 cfg, locale, alts, provide_locale_conversions[locale]
             )
             if locale in provide_locale_conversions
-            and "_LIBCPP_HAS_NO_WIDE_CHARACTERS" not in compilerMacros(cfg)
+            and ("_LIBCPP_HAS_WIDE_CHARACTERS" not in compilerMacros(cfg) or
+                 compilerMacros(cfg)["_LIBCPP_HAS_WIDE_CHARACTERS"] == "1")
             else [],
         ),
     )