We'd like to use a consistent checksum scheme everywhere so that we can:
a) incorporate archive checksums into our specs and have a
consistent hashing algorithm across all specs.
b) index mirrors with a consistent type of checksum, and not one that
is dependent on how spack packages are written.
- [x] convert existing md5, sha224, sha512, sha1 checksums to sha256
- 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
Several packages specified pkg-config as a dependency, which is
a specific implementation of the pkgconfig virtual. Most packages
do not request a specific implementation. The current concretizer
may choose a different implentation of pkgconfig for the nonspecific
dependents, which conflicts with the request for pkg-config. This
replaces all requests for a specific implementation of pkgconfig
with the virtual package as a temporary solution to the issue.
