Supporting multiple platforms is simple. Assume the user has an existing build pipeline and you need to integrate into it. That means doing one of:

1) provide a single, amalgamated .h/.cpp pair 2) provide per-platform, per-config precompiled static and/or dynamic libs 3) provide all dependencies in the form of 1 or 2

Voila! Your goal should be to provide something that can be trivially added to an existing pipeline.