Track install path type in receipt

[mistydemeo]

Right now, we have some slightly complex logic around path handling with the install prefix. This comes from the fact that we don't know whether it's a cargo home style path or not; cargo home uses an install prefix-style location, with subdirectories, while other methods don't, which means the two methods require slightly different logic. It would be great to replace our current heuristics with actual information we can branch on.