RFR: 8274244: ReportOnImportedModuleAnnotation.java fails on rerun

[Joe Darcy]

In terms of jtreg build tags, semantically this test wants to:

* build annotation processing sources
* compile module sources, running build annotation processor

In particular, the test wants to always compile the module sources, even if class files are newer than the module-info.java files. Since the test is not written in terms of those tags, I've added a pre-step which delete any existing class files from the output directory. If needed, some extra care could be taken to only delete files from the one module.

With this addition, the test will pass even when run with an already populated JTwork directory. At present, the test fails since the implicit compilation of module-info.java is *not* done when the class files in the output directory are newer than the sources.

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Commit messages:
 - 8274244: ReportOnImportedModuleAnnotation.java fails on rerun

Changes: https://git.openjdk.java.net/jdk/pull/5802/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=5802&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8274244
  Stats: 19 lines in 1 file changed: 18 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5802.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5802/head:pull/5802

PR: https://git.openjdk.java.net/jdk/pull/5802