Print detailed error information when opening cmd pipe/socketpair fails
Retrieve and print detailed information using GetLastError() and
strerror().
This should be more useful to end-users than the current message (simply
“Error opening cmd pipe”) and might have helped us to solve
https://gitlab.com/openconnect/openconnect/-/issues/228 more quickly.
Signed-off-by: Dimitri Papadopoulos <3350651-DimitriPapadopoulos@users.noreply.gitlab.com> Signed-off-by: Daniel Lenski <dlenski@gmail.com>