def METHOD_NAME(self):
    spec = self.spec
    # For build notes see https://wiki.fysik.dtu.dk/gpaw/install.html
    libxc = spec["libxc"]
    blas = spec["blas"]
    lapack = spec["lapack"]
    python_include = spec["python"].headers.directories[0]
    numpy_include = join_path(
        spec["py-numpy"].prefix, spec["python"].package.platlib, "numpy", "core", "include"
    )
    libs = blas.libs + lapack.libs + libxc.libs
    include_dirs = [
        python_include,
        numpy_include,
        blas.prefix.include,
        lapack.prefix.include,
        libxc.prefix.include,
    ]
    if "+mpi" in spec:
        libs += spec["mpi"].libs
        mpi_include_dirs = repr([spec["mpi"].prefix.include])
        mpi_library_dirs = repr(list(spec["mpi"].libs.directories))
        include_dirs.append(spec["mpi"].prefix.include)
    if "+scalapack" in spec:
        libs += spec["scalapack"].libs
        include_dirs.append(spec["scalapack"].prefix.include)
        scalapack_macros = repr(
            [("GPAW_NO_UNDERSCORE_CBLACS", "1"), ("GPAW_NO_UNDERSCORE_CSCALAPACK", "1")]
        )
    if "+fftw" in spec:
        libs += spec["fftw"].libs
        include_dirs.append(spec["fftw"].prefix.include)
    if "+libvdwxc" in spec:
        libs += spec["libvdwxc"].libs
        include_dirs.append(spec["libvdwxc"].prefix.include)
    lib_dirs = list(libs.directories)
    libs = list(libs.names)
    rpath_str = ":".join(self.rpath)
    if spec.satisfies("@:19.8.1"):
        cfgfile = "customize.py"
    else:
        cfgfile = "siteconfig.py"
    with open(cfgfile, "w") as f:
        f.write("libraries = {0}\n".format(repr(libs)))
        f.write("include_dirs = {0}\n".format(repr(include_dirs)))
        f.write("library_dirs = {0}\n".format(repr(lib_dirs)))
        f.write("extra_link_args += ['-Wl,-rpath={0}']\n".format(rpath_str))
        if "+mpi" in spec:
            f.write("define_macros += [('PARALLEL', '1')]\n")
            f.write("compiler='{0}'\n".format(spec["mpi"].mpicc))
            f.write("mpicompiler = '{0}'\n".format(spec["mpi"].mpicc))
            f.write("mpi_include_dirs = {0}\n".format(mpi_include_dirs))
            f.write("mpi_library_dirs = {0}\n".format(mpi_library_dirs))
        else:
            f.write("compiler='{0}'\n".format(self.compiler.cc))
            f.write("mpicompiler = None\n")
        if "+scalapack" in spec:
            f.write("scalapack = True\n")
            f.write("define_macros += {0}\n".format(scalapack_macros))
        if "+fftw" in spec:
            f.write("fftw = True\n")
        if "+libvdwxc" in spec:
            f.write("libvdwxc = True\n")