Ah, my blind eye, it's obvious what the problem is, the static libraries that really require -ldl and -lpthread (libLLVMSupport.a) are listed _AFTER_ -l{dl,pthread}
Ah, my blind eye, it's obvious what the problem is, the static libraries that really require -ldl and -lpthread (libLLVMSupport.a) are listed _AFTER_ -l{dl,pthread}