RFR: 7902762: JMH: Use "blackhole" compiler command

[Aleksey Shipilev]

JMH can be enabled to use the "blackhole" compile command from [JDK-8252505](https://bugs.openjdk.java.net/browse/JDK-8252505).

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Commit messages:
 - 7902762: JMH: Use "blackhole" compiler command

Changes: https://git.openjdk.java.net/jmh/pull/8/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jmh&pr=8&range=00
  Issue: https://bugs.openjdk.java.net/browse/CODETOOLS-7902762
  Stats: 207 lines in 15 files changed: 108 ins; 38 del; 61 mod
  Patch: https://git.openjdk.java.net/jmh/pull/8.diff
  Fetch: git fetch https://git.openjdk.java.net/jmh pull/8/head:pull/8

PR: https://git.openjdk.java.net/jmh/pull/8