bottle: use File.lutime instead of system call

[dtrodrigues]

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Now that Ruby has File.lutime included (https://ruby-doc.org/core-2.5.0/File.html#method-c-lutime) in versions that are older than the minimum Ruby version required by Homebrew, use File.lutime instead of the touch system call.

[MikeMcQuaid]

Very nice 👏🏻