Add back spack directory

spack/.gitignore

spack/README.md

spack/packages/dawn/exec.patch

spack/packages/dawn/install.patch

spack/packages/dawn/package.py

spack/packages/dawncut/install.patch

spack/packages/dawncut/package.py

spack/packages/dd4hep/package.py

spack/packages/dd4hep/tbb-workarounds.patch

spack/packages/dd4hep/tbb2.patch

spack/packages/eicd/package.py

spack/packages/fmt/fmt-attributes-cpp11_4.1.0.patch

spack/packages/fmt/fmt-no-export-cpp11flag_3.0.0.patch

spack/packages/fmt/fmt-use-cmake-cxx-standard_3.0.0.patch

spack/packages/fmt/package.py

spack/packages/geant4/CLHEP-10.03.03.patch

spack/packages/geant4/cxx17.patch

spack/packages/geant4/cxx17_geant4_10_0.patch

...ackages/geant4/geant4-10.4.3-cxx17-removed-features.patch

spack/packages/geant4/package.py