[Bug libstdc++/107511] [13 Regression] gcc-13-20221030 failure to build on Cygwin due to lack of secure_getenv

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107511

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Sigh, this is what I get for using AC_CHECK_FUNCS(secure_getenv) instead of
writing my own check that would actually do the right thing.