[PATCH] localedata: Avoid concurrently written locales in gen-locale.sh

[Florian Weimer]

* Adhemerval Zanella Netto:

> Looks good to me. Just curious Florian, how did you notice this issue?

Tests which use locales are occasionally failing on cfarm120.osuosl.org,
a POWER10 machine with 192 hardware threads.  Typically, there is
one test failure per run.  It's not always the same test.

Thanks,
Florian