RFR: 8325316: Enable -pedantic -Wpedantic for gcc

[Julian Waters]

Similarly to [JDK-8325163](https://bugs.openjdk.org/browse/JDK-8325163), this enables pedantic mode for gcc, ensuring stricter Standard conformance and allowing for buggy and broken code previously undetectable by gcc to be caught

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Commit messages:
 - Semicolon in compilerWarnings_gcc.hpp
 - compilerWarnings_gcc.hpp
 - 8325316

Changes: https://git.openjdk.org/jdk/pull/17727/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=17727&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8325316
  Stats: 5 lines in 2 files changed: 3 ins; 1 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/17727.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17727/head:pull/17727

PR: https://git.openjdk.org/jdk/pull/17727