Delete also the directories specified in <targetPath>

[desruisseaux]

Each <source> element (new in Maven 4) can have an optional <targetPath> element. If this element is specified, it should also be deleted by the Maven Clean Plugin. This change completes the current Maven 3 behaviour, which deletes also the directories specified by the <sourceDirectory> and <testSourceDirectory> elements.

This pull request also modifies the list of directories for removing redundancies. For example, if the plugin deletes the target directory, there is no need to keep an entry for the target/classes directory. Likewise, the reportDirectory field is removed because its value (read-only) was identical to outputDirectory (also read-only). A side effect of this change is that the following logs, which was previously emitted by the default integration test, are now gone:

[DEBUG] Skipping non-existing directory (…snip…)/target/it/default/target/classes
[DEBUG] Skipping non-existing directory (…snip…)/target/it/default/target/test-classes
[DEBUG] Skipping non-existing directory (…snip…)/target/it/default/target/classes

[slawekjaranowski]

can we add a test for it?

[desruisseaux]

Oups! Right, I forget that. Will do this weekend.

[desruisseaux]

Added the integration test. Also modified the code for resolving relative paths against ${maven.build.outputDirectory} (usually target/classes), as specified in maven.mdo.

Note: this change assumes that apache/maven#11322 is accepted, i.e. that the specification in maven.mdo is incomplete and should said that relative paths are rather resolved against ${maven.build.testOutputDirectory} when the scope is test.

[github-actions]

@desruisseaux Please assign appropriate label to PR according to the type of change.