Runtime CPU constraints

[mmdriley]

Some of our demos (e.g. Meltdown-DE) are microarchitecture-specific, which is something we can't test for at compile time. We could consider using a library like https://github.com/google/cpu_features to retrieve vendor and microarchitecture information and provide useful diagnostics.

[asteinha]

Most of our Meltdown examples are microarchitecture-specific. Beginning with the original Meltdown (Meltdown-US) that does not work on AMD.