[Bug libstdc++/111726] lgamma usage in std::poisson_distribution could cause a Data race

[redi at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111726

--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Jonathan Wakely from comment #2)
> We should use the non-standard but thread-safe lgamma_r if available.

And if not available, we can use std::log(std::abs(std::tgamma(x))).