- may need some tweaks to confirm/correct which interface is used

- match current style on cooley and bebop
- set explicit HOME to avoid interference from user spack env

- update to newer mpich
- find new compilers automatically, and display them
- force use of gcc 7.x

- also update yaml to build fewer spack packages

- requires 'udreg' memory registration method
- works with libfabric 1.7
- use patches for now until changes upstreamed
- packages.yaml tweaked to reduce build time

- also normalize labels for test runs with bebop scripts

- 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