os: remove incorrect detection of O_CLOEXEC flag on darwin
The below range loop will not stop when encountering
the first '.' character in a Darwin version string like "15.6.0".
for i = range osver {
if osver[i] != '.' {
continue
}
}
}
Therefore, the condition i > 2 was always satisfied and
supportsCloseOnExec was always set to true.
Since the minimum supported version of OSX for go is currently 10.8
and O_CLOEXEC is implemented from OSX 10.7 on the detection code
can be removed and support for O_CLOEXEC is always assumed to exist.