ctime, localtime, tzset, wcsftime: Fix env access (regr. 2024-02-09). Reported by Markus Mützel <markus.muetzel@gmx.de> in <https://lists.gnu.org/archive/html/bug-gnulib/2024-04/msg00457.html>. * lib/ctime.c (rpl_ctime): Fix logic of environment traversal. * lib/localtime.c (rpl_localtime): Likewise. * lib/tzset.c (rpl_tzset): Likewise. * lib/wcsftime.c (rpl_wcsftime): Likewise.