Use `errno` instead, which is icky, but given that all of the failure
modes are from POSIX I/O functions, it’s at least in keeping with them.
This is a major API break.
Signed-off-by: Philip Withnall <withnall@endlessm.com>
Helps: #40
It has previously been implicitly pulled in by libsysprof-capture, but
that will change in future.
Signed-off-by: Philip Withnall <withnall@endlessm.com>
Helps: #40
