const golang.org/x/sys/unix.SYS_DUP2

one use

	golang.org/x/sys/unix (current package)
		zsysnum_darwin_arm64.go#L75: 	SYS_DUP2                           = 90

The pages are generated with Golds v0.2.8-preview. (GOOS=darwin GOARCH=arm64)