Instructions on how to use library at compile time

[travisdowns]

There are demo snippets in the README showing how to use the library at the source level, and there is a building with cmake part about building it, but it would be nice to have a section that explains how to actually to add the library to your build: e.g., do you need to link against any binary? or just include the header?

You cover how a project using cmake should consume this, but a large number of projects aren't using cmake, so even though they'll build cpu_features itself with cmake, they should be able to then integrate the output into their own build system.

I guess one or two lines about that scenario would suffice.