- will open PR for spack for long term fix

- use local pwd for tmp files (easier cleanup in CI environments)
- manually generate repos.yaml without perturbing ~/.spack
- copy packages.yaml into place without perturbing ~/.spack

- fix bug in previous tmp dir settings
- auto generate repos.yaml to avoid polluting ~/.spack

- will be easier to clean up in jenkens/ci environments

- this is safer for use in environments like continuous integration where we don't want to
  perturb any persistent configuration

- better packages.yaml example to leverage existing modules
- use sds-tests instead of ssg benchmarks