I found out the reason for the crash. My file system is case sensitive (not default in OS X). The file could not be found because VHACD.Build.cs referred to the file with wrong case (/lib/ vs /Lib/).
This crash is fixed in 660ab7f0c9d34a5772d9e7dad80e63be54ecae65
Btw, that commit is HUGE (648 290 lines!), why the hell would someone allow commits like that. You can’t trace history or even diff it in a reasonable way. Please find the person responsible for stuff like that and pour some cold water over his/her head.