- remove the old LGPL license headers from all files in Spack
- add SPDX headers to all files
- core and most packages are (Apache-2.0 OR MIT)
- a very small number of remaining packages are LGPL-2.1-only
nghttp2 depends on python, and requires the install directory to exist,
and contain the python module directory which it will eventually
install the python modules into.
