[Bug libobjc/63765] [5.0 Regression] libobjc testsuite failures on AIX caused by setting _XOPEN_SOURCE

[dje at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63765

--- Comment #7 from David Edelsohn <dje at gcc dot gnu.org> ---
Yes, the single objc failure existed before the patch. But I don't know if
*other* targets need _XOPEN_SOURCE=500.