`elastic-package build` could exclude `.DS_Store` files gracefully on macOS

[jmcarlock]

When building packages with elastic-package build with macOS, a common pain point is that system generated hidden files (specifically .DS_Store) cause it to generate errors when building packages if the folder has been opened with Finder. Instead of generating an error, these files could be automatically excluded from the package build.

These files seem to already be excluded from the package root directory, but not subdirectories.

[mrodm]

These files seem to already be excluded from the package root directory, but not subdirectories.

This is not detected by the validation since it is allowed to have additional files in the root directory:
https://github.com/elastic/package-spec/blob/77bd5412585cbbce62afb7de1fe12168c55b3aa7/spec/integration/spec.yml#L7

[jmcarlock]

Thank you, @mrodm , This is a big QOL improvement!