[jdk8u-dev] RFR: 8307531: [aarch64] JDK8 single-step debugging is extremely slow

[Sergey Nazarkin]

This fix removes a workaround from the early days of aarch64 port development.  Not sure what the original reason was (@theRealAph could you please check?), now it literally blocks debugging on linux_aarch64. 

On the test (attached to jira) single step takes about 30s, while the debugerless run completes in 3s. jdk11+ is free of this bug.

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Commit messages:
 - 8307531: [aarch64] JDK8 single-step debugging is extremely slow

Changes: https://git.openjdk.org/jdk8u-dev/pull/313/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk8u-dev&pr=313&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8307531
  Stats: 8 lines in 2 files changed: 1 ins; 7 del; 0 mod
  Patch: https://git.openjdk.org/jdk8u-dev/pull/313.diff
  Fetch: git fetch https://git.openjdk.org/jdk8u-dev.git pull/313/head:pull/313

PR: https://git.openjdk.org/jdk8u-dev/pull/313