RFR: CODETOOLS-7902872: jcstress: check for C1/C2 availability and adjust configurations

[Aleksey Shipilev]

Split compilation and other VM modes would futilely try to use C1 or C2 when not available. This affects Zero VM (has no C1/C2) and Minimal VM (has only C1). jcstress should autodetect the compiler availability and adjust itself accordingly.

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Commit messages:
 - Remove excess import
 - CODETOOLS-7902872: jcstress: check for C1/C2 availability and adjust configurations

Changes: https://git.openjdk.java.net/jcstress/pull/22/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jcstress&pr=22&range=00
  Issue: https://bugs.openjdk.java.net/browse/CODETOOLS-7902872
  Stats: 287 lines in 7 files changed: 109 ins; 32 del; 146 mod
  Patch: https://git.openjdk.java.net/jcstress/pull/22.diff
  Fetch: git fetch https://git.openjdk.java.net/jcstress pull/22/head:pull/22

PR: https://git.openjdk.java.net/jcstress/pull/22