RFR: JDK-8314975: JavadocTester should set source path if not specified

[Hannes Wallnöfer]

On Fri, 25 Aug 2023 00:30:23 GMT, Jonathan Gibbons <jjg at openjdk.org> wrote:

> Please review a test-only fix, for `JavadocTester`, to set the source path to a sensible value if none specified explicitly, to override the tool default to use the class path.
> 
> The underlying issue is that TestNG is on the class path, and contains a file `Version.java` in the root directory -- i.e. the unnamed package. This can interfere with various tests that use classes in the unnamed package.
> 
> The fix is to set the source path to `testSrc`, so that `testng.jar` is never on the source path.

Marked as reviewed by hannesw (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/15424#pullrequestreview-1629275045