tests: use spate and not Spate on Hopper

Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
scripts: add build script for NERSC Hopper (Cray XE6)

Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
tests: simplify spate launcher on Hopper

Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>