Launching UE4 (built from source) crashes on OSX

I’m using UE4.19.2 for legacy reasons, and I’m trying to build my project on OSX High Sierra. I’ve followed the build instructions on GitHub to the letter, but when I do project>run in XCode, the editor appears to crash and is unresponsive at “Initialising…35%”. I thought this might just be working behind the scenes, but after 24 hours there is no change.

Lot’s of posts seem to point towards deleting DerivedDataCache, but this folder is empty.

The last log item is consistently:

2019-05-22 14:44:19.308397+0100 ShaderCompileWorker[95927:1290424] [2019.05.22-13.44.19:308][  0]LogDerivedDataCache: Unable to find inner node Shared for hierarchical cache Hierarchy.