[tlbuild] Success of tests/bibtexu-{sort, char}.test depends on locale

[Johannes Hielscher]

Dear TL builders & BibTeX maintainers,


I'm on r65664, platform aarch64-linux. The TL test suite recently got
triggered on two bibtexu tests:

FAIL: tests/bibtexu-sort
FAIL tests/bibtexu-sort.test (exit status: 4)
FAIL: tests/bibtexu-char
FAIL tests/bibtexu-char.test (exit status: 14)


The following files differ (wrongly ordered lines) between the output
as processed by the newly compiled binary, and the reference in the
texk/bibtex-x/tests directory:

# tests/bibtexu-sort
caseu.bbl

# tests/bibtexu-char
charu.bbl
nameu.bbl
periodu.bbl
substru.bbl
txtprfxu.bbl
widthu.bbl


It turns out that the success of these tests critically depends on the
locale setting at test run time. If I run the test suite on the
en_US.UTF-8 locale, above tests fail, but with an `export LC_ALL=C`
beforehand, everything passes just fine.

I haven't observed this behaviour in the past (TL2022 build season and
earlier); it might be related to the recent changes to bibtexu and/or
OS updates (I'm on Debian 10 aka buster aka oldstable, but who knows?).

Expected behaviour: FWIW tests should not fail, when the environment
bothers them with language settings as exotic as en_US.UTF-8 . Rather,
they should be insensitive of OS settings, or set up their own locale
ad-hoc.


Best,
Johannes