RFR: 8350280: The JDK-8346050 testlibrary changes break the build

[Leonid Mesnik]

Please review following trivial PR that fix library build by adding --add-exports. 
Testing: tier1

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Commit messages:
 - Added javac opts

Changes: https://git.openjdk.org/jdk/pull/23680/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23680&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8350280
  Stats: 1 line in 1 file changed: 1 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/23680.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23680/head:pull/23680

PR: https://git.openjdk.org/jdk/pull/23680