`uv__open_cloexec()` already returns a libuv error code in case
of failure, and not `-1` like syscalls do.
Fixes: https://github.com/nodejs/help/issues/2099
PR-URL: https://github.com/libuv/libuv/pull/2645
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Saúl Ibarra Corretgé <saghul@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Jameson Nash <vtjnash@gmail.com>