...as setting a GNU Make LANG var exports it to recipes as an env var, and see
e.g. 56bc0b1a "Don't set locale env vars on
macOS" for potential problems caused by that.

This is the core half of a change spanning the core and help repos.

Change-Id: Ib7ae3b6edcef0b70e211a01aad4b3bd5c8905e06
Reviewed-on: https://gerrit.libreoffice.org/70929
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>