Xcodebuild and different build flavours for AAX

The plugin I’m making has both an instrument version and an effect version. I’m trying to make a bash script to call xcodebuild and pass in JucePlugin_IsSynth=1/0 via GCC_PREPROCESSOR_DEFINITIONS. This works great for VST and AU, but it doesn’t seem to work for AAX.
This I’m guessing is because AAX should have a different JucePlugin_AAXCategory depending on if they’re synths or effects. However, if I pass in JucePlugin_AAXCategory via GCC_PREPROCESSOR_DEFINITIONS, it seems to have no effect. Doing the same thing in xcode works perfectly.

Can you offer some advice for how to build separate ‘flavours’ of a plugin? I would use Projucer but ‘is synth’ is at the project level and can’t be defined per configuration.