DSDLDefinition: do not resolve symlink

[filippobrizzi]

Remove path resolution for files.
To make pydsdl work with Bazel we need to allow it to work with symlinks as Bazel works with sandbox environments.

[pavel-kirienko]

Have you ascertained that this change alone is sufficient to make it work with Bazel? Symlink resolution is not essential for PyDSDL, but path canonicalization is, so that should be introduced instead.

[filippobrizzi]

@pavel-kirienko to be honest, I didn't do a deep investigation of every possible Bazel use case, but just the minimal changes to make my specific case work:
Run nnvg tool to generate C++ code from dsdl files.

Also, if you will ever be interested in adding Bazel support to dsdl C++ code generation, let me know as I can share some Bazel code that can serve as starting point.

[pavel-kirienko]

@thirtytwobits is this going to break anything on your side?

[thirtytwobits]

Yes. This was added to fix #111
I'm not sure why it doesn't work with symlinks?

[thirtytwobits]

@filippobrizzi , can you provide an example for how this code fails when the path includes a symlink?

[thirtytwobits]

Is this really about symlinks or are we asking to allow relative paths to be canonical?