and my_getwd(). The cause is my_errno define which
depends on my_thread_var being a not null pointer
otherwise it will be de-referenced and cause
a SEGV already in the signal handler.

Replace uses of these functions in the output_core_info
using posix read/getcwd functions instead.

The getwd fallback in my_getcwd isn't needed as
its been obsolute for a very long time.

Thanks Vladislav Vaintroub for diagnosis and posix
recommendation.