RFR: CODETOOLS-7902857: jcstress: Support split compilation modes [v2]

[Aleksey Shipilev]

> The groundwork that uses CompilerDirectives facility finally allows us to compile the actor methods with different compilers. This should catch inconsistencies in different compilers using incompatible memory barrier schemes.

Aleksey Shipilev has updated the pull request incrementally with one additional commit since the last revision:

  Refactor code a little bit

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Changes:
  - all: https://git.openjdk.java.net/jcstress/pull/16/files
  - new: https://git.openjdk.java.net/jcstress/pull/16/files/9eda0b0b..4c682a78

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jcstress&pr=16&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jcstress&pr=16&range=00-01

  Stats: 51 lines in 7 files changed: 31 ins; 15 del; 5 mod
  Patch: https://git.openjdk.java.net/jcstress/pull/16.diff
  Fetch: git fetch https://git.openjdk.java.net/jcstress pull/16/head:pull/16

PR: https://git.openjdk.java.net/jcstress/pull/16