[newlib-cygwin/main] Revert "Cygwin: locales: drop supporting iso639 strings as valid locales"

[Corinna Vinschen <corinna@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=7002f7f7c7d15f81444f00b0f606c750a9edfc53

commit 7002f7f7c7d15f81444f00b0f606c750a9edfc53
Author:     Corinna Vinschen <corinna@vinschen.de>
AuthorDate: Sat Mar 25 22:28:25 2023 +0100
Commit:     Corinna Vinschen <corinna@vinschen.de>
CommitDate: Sat Mar 25 22:30:15 2023 +0100

    Revert "Cygwin: locales: drop supporting iso639 strings as valid locales"
    
    This reverts commit 15898b95881b1fa504e671e0bcfd653b242effa8.
    
    The idea behind this patch was wrong.  Systems are supposed to
    support iso639-only strings as settings for the locale environment
    variables, and they are not necessarily available in the
    /usr/share/locale/locale.alias file.
    
    Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

Diff:
---
 winsup/cygwin/nlsfuncs.cc | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/winsup/cygwin/nlsfuncs.cc b/winsup/cygwin/nlsfuncs.cc
index 6e2681c86150..6722dd9dd5b0 100644
--- a/winsup/cygwin/nlsfuncs.cc
+++ b/winsup/cygwin/nlsfuncs.cc
@@ -127,8 +127,17 @@ __get_rfc5646_from_locale (const char *name, wchar_t *win_locale)
   c = wcschr (locale, '_');
   if (!c)
     {
-      set_errno (ENOENT);
-      return -1;
+      /* try if the locale can be resolved from the language tag
+         fix up Linux-only locale first */
+      if (!wcscmp (locale, L"ber"))
+	wcscpy (locale, L"tzm");
+      if (ResolveLocaleName (locale, wlocale, ENCODING_LEN + 1) <= 0)
+	{
+	  set_errno (ENOENT);
+	  return -1;
+	}
+      wcpcpy (win_locale, wlocale);
+      return 1;
     }
 
   /* Convert to RFC 5646 syntax. */