RFR: 8308286 Fix clang warnings in linux code [v6]

[Artem Semenov]

> When using the clang compiler to build OpenJDk on Linux, we encounter various "warnings as errors".
> They can be fixed with small changes.

Artem Semenov has updated the pull request incrementally with one additional commit since the last revision:

  update

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/14033/files
  - new: https://git.openjdk.org/jdk/pull/14033/files/101bf062..842d33d8

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=14033&range=05
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=14033&range=04-05

  Stats: 26 lines in 5 files changed: 11 ins; 11 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/14033.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14033/head:pull/14033

PR: https://git.openjdk.org/jdk/pull/14033