scripts/build doesn't rely on git rev-parse #2701

GitHub's tag archive removes the .git folder.  This broke git rev-parse and its ability to find the root of the openscholar dir.  Instead I'm using the location of hte build script as a base for finding the root.
Merge pull request #2703 from openscholar/2701-build_for_tagged

scripts/build doesn't rely on git rev-parse #2701