[jdk17u-dev] RFR: 8341722: Fix some warnings as errors when building on Linux with toolchain clang

[Matthias Baesken]

Backport of 8341722 from 21u-dev; symtab.c coding needed manual adjustment; os_linux part of commit not in 17

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Commit messages:
 - Backport 3aa59b3139d6ca88afb4339510b0a47ec15c8959

Changes: https://git.openjdk.org/jdk17u-dev/pull/3179/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=3179&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8341722
  Stats: 8 lines in 3 files changed: 1 ins; 6 del; 1 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/3179.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev.git pull/3179/head:pull/3179

PR: https://git.openjdk.org/jdk17u-dev/pull/3179