[jdk21u-dev] RFR: 8338154: Fix -Wzero-as-null-pointer-constant warnings in gtest framework

[Goetz Lindenmaier]

I backport this for parity with 21.0.9-oracle

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Commit messages:
 - Backport d77e6fe45c7b834db457a772ce0bea514d2e44f3

Changes: https://git.openjdk.org/jdk21u-dev/pull/1742/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=1742&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8338154
  Stats: 3 lines in 2 files changed: 1 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/1742.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/1742/head:pull/1742

PR: https://git.openjdk.org/jdk21u-dev/pull/1742