autoconf test for finding UTF-8 locale?

[Werner LEMBERG]

Sorry for abusing a bug mailing list for a user question but it seems
that 'gettext' doesn't have any other related channel.

I'm searching for an autoconf test that checks whether a 'neutral'
locale with UTF-8 encoding is available.  Interestingly, the
'autoconf-archive' git repository doesn't have such a thing, which
surprises me because many tools behave differently depending on
one-byte or multi-byte encodings (for example, GNU `awk` or `perl`).

According to

  
https://unix.stackexchange.com/questions/597962/how-widespread-is-the-c-utf-8-locale

I can't assume that 'C.UTF-8' is universally available; it seems that
it is necessary to also check for 'en_US.UTF-8'.  How can this be done
in a generic way that works on as many platforms as possible?

Please advise.


   Werner