RFR: 8256618: Zero: Linux x86_32 build still fails [v4]

[Aleksey Shipilev]

> There is no os::workaround_expand_exec_shield_cs_limit symbol available:
> 
> 
> collect2: error: ld returned 1 exit status
> 
> That symbol is defined in `os_linux_x86.cpp`, which is not available to Zero that builds `os_linux_zero.cpp`.
> [JDK-8248271](https://bugs.openjdk.java.net/browse/JDK-8248271) added the declaration to `os_linux_zero.hpp`, but that is not enough, because the definition is still missing. I propose we move the definition up the hierarchy, to `os_linux.cpp` and protect it firmly with `IA32`.
> 
> Additional testing:
>  - [x] Linux {x86_32, x86_64} server builds
>  - [x] Linux {x86_32, x86_64} zero builds

Aleksey Shipilev has updated the pull request incrementally with one additional commit since the last revision:

  Put the #ifdef to protect the comment too

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/1310/files
  - new: https://git.openjdk.java.net/jdk/pull/1310/files/a72ee0a1..57ffe333

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=1310&range=03
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=1310&range=02-03

  Stats: 2 lines in 1 file changed: 1 ins; 1 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1310.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1310/head:pull/1310

PR: https://git.openjdk.java.net/jdk/pull/1310