[SystemZ][z/OS] Define _LIBCPP_ELAST

The aim is to define _LIBCPP_ELAST for z/OS libc++ since strerror/strerror_r can't handle out-of-range errno values.

Differential Revision: https://reviews.llvm.org/D98541

GitOrigin-RevId: 62705ee012578584b83e94a2dc9788c332f53a66
1 file changed