Dynamically Check Kernel Version

[kavon]

Currently we have a compile-time check of a minimum kernel version when building halomon for feature compatibility.

The problem is that when distributing halo executables or the docker image*, the new minimum kernel version is equal to the version used by the system that compiled the halomon library. Thus, we need a dynamic check through uname (see man 2 uname) to ensure that halomon's sampling system is still compatible with the currently executing system.

*Docker does not capture properties of the kernel in its image