Spack config on MacOS

packages.yaml

packages:
    # gcc:
    #     paths:
    #         gcc@4.9.4%gcc@4.4: /usr/local
    #     buildable: False
    #     version: [4.9.4]

    llvm:
        paths:
            llvm@8.0.0-apple%gcc@4.4: /usr/local
        buildable: False
        version: [8.0.0-apple]

    cmake:
        paths:
            cmake@3.12.1: /usr/local
        buildable: False
        version: [3.12.1]

    gmsh:
        paths:
            gmsh@3.0.6: /usr/local
        buildable: False
        version: [3.0.6]

    py-cython:
        paths:
            py-cython@0.28.5: /usr/local/opt/cython
        buildable: False
        version: [0.28.5]

    autoconf:
        paths:
            autoconf@system: /usr/local
        buildable: False
        version: [system]

    automake:
        paths:
            automake@system: /usr/local
        buildable: False
        version: [system]

    libtool:
        paths:
            libtool@system: /usr/local
        buildable: False
        version: [system]

    openssl:
        paths:
            openssl@system: /usr/local
        buildable: False
        version: [system]

    flex:
        paths:
            flex@system: /usr/local
        buildable: False
        version: [system]

    bison:
        paths:
            bison@system: /usr/local
        buildable: False
        version: [system]

    pkg-config:
        paths:
            pkg-config@0.29.2%clang@8.0.0-apple: /usr/local
            pkg-config@0.29.2%gcc@4.9.4: /usr/local
        buildable: False
        version: [0.29.2]

    environment-modules:
        paths:
            environment-modules@system: /usr/local
        buildable: False
        version: [system]

    python:
        paths:
            python@2.7.10: /System/Library/Frameworks/Python.framework/Versions/2.7
        buildable: False
        version: [2.7.10]

    hdf5:
        paths:
            hdf5@1.10.3: /usr/local
        buildable: False
        variants: ~fortran+hl
        version: [1.10.1]

    zlib:
        paths:
            zlib@1.2.11: /usr/local
        buildable: False
        version: [1.2.11]

    qt:
        paths:
            qt@5.5.1: /usr/local/Cellar/qt55/5.5.1
        buildable: False
        version: [5.5.1]

    mpich:
        paths:
            mpich@3.2.1%gcc@4.9.4: /usr/local
            mpich@3.2.1%clang@8.0.0-apple: /usr/local
        buildable: False
        version: [3.2.1]

    netcdf:
        paths:
            netcdf@4.6.1: /usr/local
        buildable: False
        version: [4.6.1]

    openblas:
        paths:
            openblas@0.3.2: /usr/local
        buildable: False
        version: [0.3.2]

    boost:
        version: [1.67.0]


    steps:
        variants: +lapack+petsc+mpi
    
    tau:
        variants: ~openmp ~comm ~phase

    trilinos:
        variants: +kokkos+teuchos~amesos~hypre~superlu-dist~mumps~metis~suite-sparse
        version: [develop]

    coreneuron:
        variants: ~openmp

    all:
        compiler: [clang@8.0.0-apple]
        providers:
            mpi: [mpich]