This commit adds a 'flush' option to the createWriteStream()
family of functions.
Refs: https://github.com/nodejs/node/issues/49886
PR-URL: https://github.com/nodejs/node/pull/50093
Reviewed-By: Yagiz Nizipli <yagiz@nizipli.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Marco Ippolito <marcoippolito54@gmail.com>
