Users can now list mirrors of the main url in packages.
- [x] Instead of just a single `url` attribute, users can provide a list (`urls`) in the package, and these will be tried by in order by the fetch strategy.
- [x] To handle one of the most common mirror cases, define a `GNUMirrorPackage` mixin to handle all the standard GNU mirrors. GNU packages can set `gnu_mirror_path` to define the path within a mirror, and the mixin handles setting up all the requisite GNU mirror URLs.
- [x] update all GNU packages in `builtin` to use the `GNUMirrorPackage` mixin.
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
Prior to this commit, running `spack module refresh` with `gdbm`
installed throws the warning:
```console
==> Warning: Could not write module file [/Users/oxberry1/spack/share/spack/lmod/darwin-sierra-x86_64/Core/gdbm/1.14.1.lua]
==> Warning: --> global name 'spack_cc' is not defined <--
```
This warning is repeated for every `gdbm` installation in Spack.
The cause of the issue seems to be the same as in spack/spack (#6089):
using `spack_cc`, `spack_cxx`, or similar inside `configure_args`
causes the warnings to throw when module files are generated.
Moving the use of `spack_cc` into `setup_environment` seems to fix the
problem, even though it's a bit of a kludge.
The problem was that the configure script was not using spack's compiler
wrappers. We now pass the proper compiler wrapper using the CC argument
explicitly.
Fixes#5892.
