Main juce include file

I’m porting old utility classes to the juce infrastructure. I’ll end up with a bunch of library classes which I’ll use in various projects. I seem to have difficulties doing this with the amalgamated version of juce; or possibly I’m approaching the whole thing from the wrong angle.

Apparently "You should NOT include juce.h or juce_amalgamated.h directly in your own source files, because that wouldn't pick up the correct Juce configuration options for your app."

What do I #include in an external file which may be included in many projects, either with an arbitrary amalgamated juce or regular juce?