RFR: JDK-8326974: ODR violation in macroAssembler_aarch64.cpp

[Andrew Haley]

This is a slightly different patch from the one suggested by the bug reporter. It doesn't make any sense to export those classes globally, so I've given them internal linkage.

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Commit messages:
 - JDK-8326974: ODR violation in macroAssembler_aarch64.cpp

Changes: https://git.openjdk.org/jdk/pull/18056/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18056&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8326974
  Stats: 3 lines in 1 file changed: 3 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/18056.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18056/head:pull/18056

PR: https://git.openjdk.org/jdk/pull/18056