RFR: 7903507: jtreg runs into race conditions for multi-modules tests [v2]

[Christian Stein]

> This change puts the necessary JAR files onto the module path as (automatic) modules - without copying them. Therefore, no race condition can happen when multiple tests that require modules of test frameworks are compiling or executing in parallel.

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

  Address review comments

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Changes:
  - all: https://git.openjdk.org/jtreg/pull/161/files
  - new: https://git.openjdk.org/jtreg/pull/161/files/2d368f00..4fe4e427

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jtreg&pr=161&range=01
 - incr: https://webrevs.openjdk.org/?repo=jtreg&pr=161&range=00-01

  Stats: 9 lines in 1 file changed: 2 ins; 3 del; 4 mod
  Patch: https://git.openjdk.org/jtreg/pull/161.diff
  Fetch: git fetch https://git.openjdk.org/jtreg.git pull/161/head:pull/161

PR: https://git.openjdk.org/jtreg/pull/161