By: Tom Sydney Kerckhove <syd@cs-syd.eu>
Warn about one capability whatever asked for the parallelism The warning to compile a test suite with -threaded -rtsopts -with-rtsopts=-N only fired when the thread count was left to the capabilities. A suite run with --jobs 4 on one capability runs its tests one at a time just the same, so it never exercises the thread safety that running them in parallel is there to find, and it said nothing about that. So decide the warning from the capability count and whether the suite means to run in parallel at all, which is what oneCapabilityWarning takes. Only a synchronous run has nothing to gain from more capabilities, so only it stays quiet.