RFR: 7903160: Run self-tests for jtreg on MacOS and Windows [v2]

[Christian Stein]

> CI builds including self-tests for `jtreg` are run on Linux.
> 
> Now, they also run on MacOS and Windows.

Christian Stein has updated the pull request incrementally with one additional commit since the last revision:

  Set up JDK 11

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Changes:
  - all: https://git.openjdk.java.net/jtreg/pull/75/files
  - new: https://git.openjdk.java.net/jtreg/pull/75/files/d9589351..3349e5ed

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jtreg&pr=75&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jtreg&pr=75&range=00-01

  Stats: 6 lines in 1 file changed: 6 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jtreg/pull/75.diff
  Fetch: git fetch https://git.openjdk.java.net/jtreg pull/75/head:pull/75

PR: https://git.openjdk.java.net/jtreg/pull/75