Add rpath patching for linuxes

- Uses the patchelf executable. If it is not found, then it is installed from source as an external
  project.
- Sets rpaths to absolute install locations for now
Still trying to mitigate boost mid-installation issues
Was missing some libraries when rpath patching

Also, libtbbs are not to be patched since they have no elf.
Again trying to mitigate parallel external build issues with boost
Trying to add external option to setup.Build
Add external command-line argument
:lipstick: copy-pasted comment in TBB lookup