MavenLauncher build classpath do not process build failure

In method `spoon.support.compiler.SpoonPom#generateClassPathFile`, `invoker.execute(request)` does not process the return value, it just catch a `MavenInvocationException`. But actually, when the return value contains a non-zero exit code, it represents maven build failure.


Start in spoon.support.compiler.SpoonPom#generateClassPathFile and inspect how invoker.execute(request) is handled alongside MavenInvocationException. Verify how the returned result represents a non-zero exit code, and consider the issue complete when Maven build failures from that result are handled rather than ignored.

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