- 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
* mpest: new package
* adding architecture env var and making more version-flexible
* fixing environment
* fixed build directory
* getting rid of duplicated code
