BinDeps is, at it's heart, a way to ensure that dependencies are satisfied. Compiling things is just a byproduct of trying to satisfy unmet dependencies. By far, the most typical dependency is a library dependency, but if you don't actually use a library, then you shouldn't use the `library_dependency` function from BinDeps. Perhaps we need a generic `file_dependency` or `binary_dependency` or something that is considered not satisfied as long as the file does not exist.
We could pretty easily build a python build step off of that if it existed. -E
