- 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
* Customization for make targets in build and test phases for AutotoolsPackage
* Updated Blitz++ to use customized make build and test targets
* Removed flake8 error
* Removed make test customization, added make install customization, need to figure out issues with multiple make targets
* Changed build_targets and install_targets to normal attributes
Modifications :
- added EditableMakefile to PackageBase subclasses
- astyle modified as an example
- preliminary hook to stop at a certain phase of install