Properly update hash in version file when building from subdirs

Created by: aprokop

Before, if one ran make from a subdirectory, the record_hash command was not run, and thus hash was not updated. Thus, if you stayed in the same subdirectory, but switched branches/hashes, the executable kept having the same hash (unless checkout also touched CMakeLists.txt).

This commit fixes it by making ArborX target depend on always-out-of-date record_hash target.

Fix #264 (closed).