RFR: JDK-8328589: unify os::breakpoint among posix platforms

[Matthias Baesken]

Seems we can unify os::breakpoint among the posix platforms supported in OpenJDK.

-------------

Commit messages:
 - JDK-8328589

Changes: https://git.openjdk.org/jdk/pull/18395/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18395&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8328589
  Stats: 44 lines in 4 files changed: 11 ins; 33 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/18395.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18395/head:pull/18395

PR: https://git.openjdk.org/jdk/pull/18395