RFR: 8327885: runtime/Unsafe/InternalErrorTest.java enters endless loop on Alpine aarch64

[Dmitry Cherepanov]

[JDK-8322163](https://bugs.openjdk.org/browse/JDK-8322163) replaced memset with a for loop on Alpine. This fixed the test on Alpine x86_64 but it enters endless loop on Alpine aarch64.

The loop causes SIGBUS to be generated and the signal handler continues to the next instruction. As gcc generates strb with auto-increment on aarch64, the increment will be skipped.

The patch makes the counter volatile to prevent compilers from generating strb with auto-increment. With the patch, the test passes on Alpine aarch64.

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Commit messages:
 - 8327885: runtime/Unsafe/InternalErrorTest.java enters endless loop on Alpine aarch64

Changes: https://git.openjdk.org/jdk/pull/18262/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18262&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8327885
  Stats: 3 lines in 1 file changed: 2 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/18262.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18262/head:pull/18262

PR: https://git.openjdk.org/jdk/pull/18262