New comment by ericonr on void-packages repository

https://github.com/void-linux/void-packages/pull/27936#issuecomment-760490117

Comment:
Ok, this probably worked for you on glibc. Since this is C++, what happens (on Linux, with pibstdc++) is that `_GNU_SOURCE` is defined. On glibc, this means a bunch of other macros (including some which that ifdef forest tests for) are defined. On musl, `_GNU_SOURCE` being defined just stays that way, so none of the macros expected by the ifdefs are there, and it ends up using `gmtime`. The patch suggestion above should fix it.