Currently we persist the tempDir when writing resumable index build state to disk, but we can get away without this. It may even provide confusing semantics in the case that a user performs a clean shutdown during an index build in the collection scan or bulk load phases, moves the database files, and starts the server back up with the new dbpath specified. Since the Sorter info is stored in dbpath/_tmp/, it is likely a safe assumption that the Sorter info was moved along with the rest of the database files. Thus, it makes the most sense to always use dbpath/_tmp/ rather than storing the tempDir.