add mingw64 to mingw-w64-cppwinrt

[ReenigneArcher]

replacement for #20003

[psyke83]

I think I can help shed some light on the situation. In Sunshine and the regex-issue testcase we are setting the locale to .utf-8, but some debugging reveals that MINGW64 fails to set it correctly, leaving it as the default (C).

Results using my fork of: https://github.com/FrogTheFrog/regex-issue

MINGW64:

setlocale info: C
Before regex
After regex. Took 0ms

UCRT64:

setlocale info: English_Ireland.utf8
Before regex
After regex. Took 194383ms

So, @MehdiChinoune was probably correct in stating that the issue is likely to be present in MINGW64, but we're not seeing the issue simply because setlocale was not having an effect. I tried to hardcode the locale as English_Ireland.utf8, it still returns as C when built against the MINGW64 runtime, so I'm not sure what's happening.

It seems that std::regex works OK with the UCRT64 runtime if the locale is unset/set to the default C. Maybe this PR is not necessary, unless there are other major issues aside from locale?

[FrogTheFrog]

I think I can help shed some light on the situation. In Sunshine and the regex-issue testcase we are setting the locale to .utf-8, but some debugging reveals that MINGW64 fails to set it correctly, leaving it as the default (C).

Results using my fork of: https://github.com/FrogTheFrog/regex-issue

MINGW64:

setlocale info: C
Before regex
After regex. Took 0ms

UCRT64:

setlocale info: English_Ireland.utf8
Before regex
After regex. Took 194383ms

So, @MehdiChinoune was probably correct in stating that the issue is likely to be present in MINGW64, but we're not seeing the issue simply because setlocale was not having an effect. I tried to hardcode the locale as English_Ireland.utf8, it still returns as C when built against the MINGW64 runtime, so I'm not sure what's happening.

It seems that std::regex works OK with the UCRT64 runtime if the locale is unset/set to the default C. Maybe this PR is not necessary, unless there are other major issues aside from locale?

Can confirm this. You either have to explicitly set it to C or leave it unset (as C++ sets it to C anyway). Setting it to default locale "" (empty string) would still produce the regex bug if the Windows locale is set to UTF-8 system-wide.