RFR: 7903856: apidiff: 7903837 breaks some builds

[Iris Clark]

On Wed, 2 Oct 2024 03:39:06 GMT, Jonathan Gibbons <jjg at openjdk.org> wrote:

> Please review a small but important fix for an issue handling EQUINOX_JAR in some build environments.
> 
> The underlying issue is that EQUINOX_JAR may or may not be required, depending on the configuration for DAISYDIFF.

Marked as reviewed by iris (Reviewer).

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PR Review: https://git.openjdk.org/apidiff/pull/22#pullrequestreview-2341853164