So here's something I was being lazy with before and never really fixed, because I wanted the user interface for defining package mappings to have some flexibility *and* be somewhat lazy.

When we're chmoding things and globbing over files, we were bumping directories to have eveyrone readable + executable permissions (0755).   When you glob over a set of files and create mappings (like `LinuxPackageMappings(binDir.*** x relativeTo(rootDir)), ...)`, you're including files + directories with the same set of Permissions.  However, directories need the appropriate executable bits set if you're to be able to list files inside them.

SOOOOOO......   What we may want when chmoding directories is to detect "read" permissions for user, group, world and automatically bump in executable permissions on directories.  

Again I was too lazy to do this by default.  There's also the odd scenario that someone may not want this.   So option #2 would be to modify the external *functions* people use to set up linux package mappings to create *two* objects, one for directories (with auto-executable permissions) and one with files (without adding executable permissions).   

I think I prefer plan A.   What are your thoughts?