Makefile: Ignore l10n when sorting
In thread https://gitlab.wikimedia.org/releng/cli/-/merge_requests/102#note_1718, I've known sort
depends on the l10n setting of the system, and exporting LC_ALL=C
resolves the ambiguity. C
is a special locale that is meant to be the simplest locale according to this StackExchange post. https://unix.stackexchange.com/a/87763/389523