MSVC now says this on master:
[17:48:12.446] c:\cirrus\src\backend\utils\adt\pg_locale.c(2912) :
warning C4715: 'icu_language_tag': not all control paths return a
value
CI doesn't currently fail for MSVC warnings, so it's a bit hidden.
FWIW cfbot does show this with a ⚠ sign with its new system for
grovelling through logs, which will now show up on every entry now
that this warning is in master.
