RFR: 8274394: Use Optional.isEmpty instead of !Optional.isPresent in jdk.jlink

[Mandy Chung]

On Sun, 26 Sep 2021 13:58:35 GMT, Andrey Turbanov <github.com+741251+turbanoff at openjdk.org> wrote:

> I propose to replace usages of !Optional.isPresent() with Optional.isEmpty method.
> It's makes code a bit easier to read.
> Noticing negation before long chain of method calls is hard.

LGTM

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Marked as reviewed by mchung (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/5707