- 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
* Allow types and 'any' in variant definitions.
- Previously variant values had to be a tuple or a callable predicate.
- This allows 'any' as shorthand for `lambda x: True` and type objects
as shorthand for "any value of this type".
- Makes variant definitions more readable, keeps lambdas out of
packages for common cases.
* Update packaging tutorial
* Fix bad file reference in packaging tutorial