- 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.
