[plugin] support for resources packaging on ubuntu

[sebsto]

When including resources in the package and packaging on Ubuntu, FileManager throws a FilePermission error. The docker daemon runs as root and files to be copied are owned by root while the archiver runs as the current user (ubuntu on EC2 Ubuntu). The FileManager manages to copy the files but throws an error after the copy. We suspect the FileManager to perform some kind of operation after the copy and it fails because of the root permission of the files.

See #449 (comment) for a description of the problem.

This PR contains code to reproduce the problem, a very simple workaround, and an integration test.
The workaround consists of

• trapping all errors
• verify if the error is the permission error (Code = 513)
• verify if the files have been copied or not
• if the two above conditions are met, ignore the error, otherwise re-throw it

I would rather prefer a solution that solves the root cause rather than just ignoring the error.
We're still investigating the root cause (see this thread on the Swift Forum and this issue on Swift Foundation swiftlang/swift-foundation#1125

[0xTim]

LGTM