RFR: 8338154: Fix -Wzero-as-null-pointer-constant warnings in gtest framework

[Magnus Ihse Bursie]

On Mon, 12 Aug 2024 05:25:49 GMT, Kim Barrett <kbarrett at openjdk.org> wrote:

> Please review this change to remove -Wzero-as-null-pointer-constant warnings
> produced by the gtest framework when such warnings are enabled.
> 
> Warnings from the 3rd party GoogleTest are suppressed by disabling that
> warning when compiling those files.
> 
> Testing: mach5 tier1

Build change is trivially fine.

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Marked as reviewed by ihse (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/20536#pullrequestreview-2233974704