RFR: CODETOOLS-7903152: On macOS, avoid using /usr/bin/tidy

[Iris Clark]

On Sat, 9 Apr 2022 00:16:21 GMT, Jonathan Gibbons <jjg at openjdk.org> wrote:

> Please review a simple makefile change to search for a better version of `tidy` on macOS than that in /usr/bin/tidy.
> 
> For compatibility, there is no change in the behavior on other platforms, although it might be reasonable to eventually extend the search to `/usr/local/bin/tidy` on other platforms if needed.

Marked as reviewed by iris (Reviewer).

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PR: https://git.openjdk.java.net/jtreg/pull/71