RFR: 8295666: Linux x86 build fails after 8292591

[Boris Ulasevich]

I have got build failure similar to recent [Linux aarch64](https://github.com/openjdk/jdk/pull/10265) and [Linux Alpha Zero](https://github.com/openjdk/jdk/pull/10721) failures:


src/hotspot/os/linux/systemMemoryBarrier_linux.cpp:65:18: error: 'SYS_membarrier' was not declared in this scope
   return syscall(SYS_membarrier, cmd, flags, cpu_id); // cpu_id only on >= 5.10
                  ^~~~~~~~~~~~~~ 


The failure is known to be fixed by adding missing ` SYS_membarrier` definition. The raw constant 375 is taken from the `linux-libc-dev_6.0.2-1_i386.deb' cross-compilation headers:

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

Commit messages:
 - 8295666: Linux x86 build fails after 8292591

Changes: https://git.openjdk.org/jdk/pull/10771/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=10771&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8295666
  Stats: 2 lines in 1 file changed: 2 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/10771.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10771/head:pull/10771

PR: https://git.openjdk.org/jdk/pull/10771