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
Add a package for [tree](http://mama.indstate.edu/users/ice/tree/).
It has a Makefile that hardcodes a prefix and some CFLAGS. Used
filter_file to:
- set the make variable *prefix* to `prefix`; and
- comment out their CFLAGS, just use ours....
It installs, runs on CentOS7, and uninstalls cleanly.
