- 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
* bison: Add missing build dependencies
bison also depends on cmp, which is currently not available in Spack.
* help2man: Add missing build dependency
* m4: Fix build with newer versions of glibc
* openssl: Add missing build dependency
openssl's configure script is actually a Perl script.
* texinfo: Add missing perl dependency
* diffutils: New package
* findutils: Fix build with newer versions of glibc
* mvapich2, mpich: Add missing findutils dependency
