Using copyfile(3) on macOS apparently results in situations where file
permissions are ignored. Using the same code for other UNIX-like
operating systems seems to fix the issue.
Refs: https://github.com/nodejs/node/issues/26936#issuecomment-476992597
PR-URL: https://github.com/libuv/libuv/pull/2233
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Santiago Gimeno <santiago.gimeno@gmail.com>
Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>
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