The PDBs for .exe are not included

When I first implemented the .pdb copy, I excluded the dist directory because in my first attempt I copied them to dist/bin, to include them in the installer.

But in the implementation that is in production, we ended up copying them to a separate .zip file, but I kept that -prune rule in find.

As a result, we have xul.pdb, which is the most important one, but we don't have all the various .pdb that correspond to the .exe files, which makes it impossible to debug the updater.

We should probably drop that rule and copy all the PDBs, except for tests.