[MRESOURCES-291] CopyResourcesMojo and TestResourcesMojo is NOT thread-safe

**[Jin Xu](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=xenoamess)** opened **[MRESOURCES-291](https://issues.apache.org/jira/browse/MRESOURCES-291?redirect=false)** and commented

If you try to make several sub-projects using this plugin to copy resources from some folter to a same folder, or even overwriting some files, it would crush.
I don't think this be thread-safe.
I see the codes. you are using File.mkdirs, which is actually not thread-safe. also, you are using file writing functions, which is not thread safe if multiple threads trying to write to a same file.
So I don't think it is good to annote these 2 mojos as thread-safe.
Please either remake that part, or remove the thread-safe annotation.
Or simply add a synchronized to that function might also be acceptable.

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No further details from [MRESOURCES-291](https://issues.apache.org/jira/browse/MRESOURCES-291?redirect=false)