Cray XC case added

[ChristopherBignamini]

Hello, I'm opening this (draft, for the moment) PR in order to add an additional Cray system case. Particularly, the modified code is a workaround to build MUSIC on PizDaint (Cray XC) for a CSCS user. I've used the same linux command of the existing Cray (XE6) case to identify the system in configure.ac, in order to avoid too many changes, but for sure is not the best solution: we could probably use the node interconnect technology to identify the system. If you think this PR is useful for MUSIC user community please let me know, I will try to finalize the system identification issue. Thank you!

[mdjurfeldt]

Yes, thank you. This PR would be useful.

Please fix the system identification. I'll then merge it.

Best regards,
Mikael

[ChristopherBignamini]

I've updated the system identification, by checking the hostname. The problem in using something more generic to identify the system model, like the interconnect technology which is usually model specific, is that different sites could have different software setups for MPI version, compiler wrappers, etc...

[mdjurfeldt]

I'm reluctant to identify the host system type based on the hostname. Then a better option would be to enable the user to explicitly set system type as an argument to the configure script.

Meanwhile, I'll send an email to Cray and ask them if they are aware of ways to identify a Cray XC,

But: Should we do that at all? Looking at your changes, they seem to rely on the environment variable SLURM_PROCID, so perhaps what we really (or also) should do is to check for Slurm?