FeatureRequest: rpm-spec: Specify minimum hardware requirements

[LecrisUT]

Opening a discussion related to this copr issue.

Background:

I've had a build on me take 5h with multiple timeouts when run with 2 CPU cores due to MPI + OpenMP oversubscription. While typically it only costs 1h on 4 cores.

Suggestions:

Provide a global macro where we can define the total number of CPU cores/memory etc. that a particular .spec file requires. This could be defined only once and be independent of %if statements to keep the parsing simple.