RFR: 7939: Cleanup of JDK dependencies in JMC tycho build

[Christoph Langer]

This cleans out some project settings and compilation flags to access JDK internals.

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Commit messages:
 - JMC-7939

Changes: https://git.openjdk.org/jmc/pull/444/files
 Webrev: https://webrevs.openjdk.org/?repo=jmc&pr=444&range=00
  Issue: https://bugs.openjdk.org/browse/JMC-7939
  Stats: 417 lines in 24 files changed: 38 ins; 296 del; 83 mod
  Patch: https://git.openjdk.org/jmc/pull/444.diff
  Fetch: git fetch https://git.openjdk.org/jmc pull/444/head:pull/444

PR: https://git.openjdk.org/jmc/pull/444