Improve the MAVEN build to do regression testing agains ALL relevant JREs

[aunkrig]

https://svn.code.sf.net/p/loggifier/code/de.unkrig.commons/trunk/commons-junit4/src/main/java/de/unkrig/commons/junit4/runner/MultipleJresTestClassRunner.java

should do the trick.

[karussell]

You could utilize github actions to run all tests for every new commit. It seems that https://github.com/actions/setup-java supports the necessary JDKs. See e.g. our small file to push out a new jar for every commit to github packages and you could run any mvn command there, I think. (for historical reasons we run our tests via travis CI and have not yet migrated everything to github actions)

Edit: if you like I can propose this as a pull request: karussell#1

• For JDK 6 I got "Unsupported major.minor version 51.0" (maybe the installed maven version in the image requires a higher java)
• For JDK 7 I got "Tests in error":

  CompilerTest.testSelfCompile:164->compileJanino:323->invoke1:362->invoke:373 » InvocationTarget
  JavaSourceClassLoaderTest.testJavaSourceClassLoader:76 » InternalCompiler Comp...
  ReportedBugsTest.testIssue69_IncompatibleClassChangeError_when_evaluating_against_janino9plus:1031 » Compile

• For JDK 8 I got:

  CompilerTest.testSelfCompile:165->compileJanino:323->invoke1:362->invoke:373 » InvocationTarget
  EvaluatorTest.test64kOperandStackHeight[CompilerFactory=janino] » StackOverflow
  JavaSourceClassLoaderTest.testJavaSourceClassLoader:76 » InternalCompiler Comp...

• I did not test JDK 9 and 10 as they are not widespread
• For JDK 11 I got the errors:

  CompilerTest.testSelfCompile:165->compileJanino:323->invoke1:362->invoke:373 » InvocationTarget
  EvaluatorTest.test64kOperandStackHeight[CompilerFactory=janino] » StackOverflow
  JavaSourceClassLoaderTest.testJavaSourceClassLoader:76 » InternalCompiler Comp...
  ReportedBugsTest.testIssue69_IncompatibleClassChangeError_when_evaluating_against_janino9plus:1032 » InvocationTarget

• For JDK 15 and 16-ea I got "Source option 6 is no longer supported. Use 7 or later"