Print spack concretization output on stdout and a separate log file

[rfhaque]

Currently benchpark setup prints the spack concretization details in <workspace-dir>/workspace/logs/setup.<time>.out file. In case of multiple experiments, this concretization log appears only once per each set of experiments built using the same config options. This makes it difficult to track compilation output for a given experiment.
If will be highly desirable to have the spack concretization output printed on the stdout and its own separate log file. Additionally, it will also be nice to have a mode like benchpark setup --dry-run which simply prints the concretization log for a given set of experiments.