add CMake option TESTS

[ranocha]

Cf. #28.

Shall we adapt the build flags before making the first release? Cf. #15.

[ranocha]

I don't understand why the linux build on Appveyor fails. There seem to be problems with the MSR registers that haven't been there before (https://ci.appveyor.com/project/ranocha/toolkiticl/builds/23065483/job/30jget4xg01si9pg#L2212).

[ranocha]

For the failed build on Linux, clinfo reports a slightly different CPU: Intel(R) Xeon(R) CPU @ 2.30GHz (failed) instead of Intel(R) Xeon(R) CPU E5-2697 v3 @ 2.60GHz (pass).

[ranocha]

Maybe reading MSR is simply not reliable on virtual platforms. I'll disable that test.

[philipheinisch]

For the failed build on Linux, clinfo reports a slightly different CPU: Intel(R) Xeon(R) CPU @ 2.30GHz (failed) instead of Intel(R) Xeon(R) CPU E5-2697 v3 @ 2.60GHz (pass).

In virtual environments, this difference is in most cases caused by simulating a generic architecture (hence no CPU type) instead of directly using the host CPU (the exact type is displayed). Virtualizing generic CPUs gives a lot more flexibility from an administrative standpoint and is preferred on most shared resource systems, as VMs can easily be moved between different host systems and the workload can be shares between different CPUs. The drawback is, that no CPU specific functions (like MSR) are available.

[philipheinisch]

Can we merge this now or do we want to add more as part of this PR?

[ranocha]

I think you can merge this now.