Also known as "chown".
The process must have the correct privileges in order to do this
successfully. The group may be changed by the owner of the file to any
group of which the owner is a member. If the owner or group is specified as
null, the ID is not changed.
pub fn setOwner(file: File, io: Io, owner: ?Uid, group: ?Gid) SetOwnerError!void
pub fn setOwner(file: File, io: Io, owner: ?Uid, group: ?Gid) SetOwnerError!void {
return io.vtable.fileSetOwner(io.userdata, file, owner, group);
}