RFR: 8254144: Non-x86 Zero builds fail with return-type warning in os_linux_zero.cpp [v3]

[Aleksey Shipilev]

> Pretty trivial: missing `return` statement for non-void returning function. GCC complains about it in 11u, but not in
> HEAD. Still, I believe we should fix it everywhere.
> Testing:
>  - [x] Linux Zero arm32 build, HEAD
>  - [x] Linux Zero arm32 build, 11u

Aleksey Shipilev has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev
excludes the unrelated changes brought in by the merge/rebase. The pull request contains three additional commits since
the last revision:

 - Merge branch 'master' into JDK-8254144-zero-non-x86-return
 - Use the common style for compiler silencing comments
 - 8254144: Non-x86 Zero builds fail with return-type warning in os_linux_zero.cpp

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/539/files
  - new: https://git.openjdk.java.net/jdk/pull/539/files/a6ea0c5d..78488b62

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=539&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=539&range=01-02

  Stats: 8688 lines in 123 files changed: 4495 ins; 3691 del; 502 mod
  Patch: https://git.openjdk.java.net/jdk/pull/539.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/539/head:pull/539

PR: https://git.openjdk.java.net/jdk/pull/539