/Library/Frameworks/Houdini.framework/Versions/9.5.175/Resources/bin/hcustom
I haven't tried it yet but you can be the first to let us know

I got curious and tried building SOP_Star. It starts but then just sits there without doing anything.
Ah, eventually it starts. Not sure why it takes so long though (few minutes). It fails on my machine though with:
ld: in /Library/Frameworks//Python.framework/Python, missing required architecture x86_64 in file