RFR: 7903160: Run self-tests for jtreg on MacOS and Windows [v21]

[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:

  Reorder steps

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

Changes:
  - all: https://git.openjdk.java.net/jtreg/pull/75/files
  - new: https://git.openjdk.java.net/jtreg/pull/75/files/086ef746..d62e2665

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jtreg&pr=75&range=20
 - incr: https://webrevs.openjdk.java.net/?repo=jtreg&pr=75&range=19-20

  Stats: 21 lines in 1 file changed: 0 ins; 15 del; 6 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