C.UTF-8 locale not available on Centos

Currently the Centos 7 release build fails due to the C.UTF-8 locale (which we use by default since b7a6b2f4) appears not to be available.

I found https://bugzilla.redhat.com/show_bug.cgi?id=902094 which seems to suggest that it may be available, but I can't work out exactly how one installs it. Only C appears in locales -a, even after removing override_install_langs=en_US from /etc/yum.conf and reinstalling glibc-common (as suggested here).

Edited Aug 24, 2020 by Ben Gamari

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