[MCOMPILER-365] Missing main classes when test contains a module descriptor

**[Christian Stein](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=sor)** opened **[MCOMPILER-365](https://issues.apache.org/jira/browse/MCOMPILER-365?redirect=false)** and commented

When `testCompile` detects a `module-info.java` file it patches the sources from the main set into the test compilation process. This yields a) recompiling main source files and b) leaves out not directly referenced main types.

I would be better to re-use _all_ compiled type from the main source set, if possible.

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**Affects:** 3.8.0

**Issue Links:**
- [MCOMPILER-341](https://issues.apache.org/jira/browse/MCOMPILER-341) Compile module-info.java files located in test sources

Start by tracing testCompile handling for a module-info.java in the test sources, focusing on how main and test source sets are combined. Check how compiled types from the main source set are selected and verify that test compilation reuses all of them without recompiling main sources or omitting indirectly referenced types.

Written by the indexing model from the issue text.