std.c (darwin) update to new opaque syntax

This was an undetected conflict between

76a195473dac059a842fed2a6ba581ca99947d2b and
95a37373e9f576854956c2909cc128b5b6388ec6
a4828f6d0fAndrew Kelley committed on 10/9/2020, 5:45:39 AMparent76a1954
1 file changedLine totals unavailable