More robust insertion point for arg_scratch

src/codegen/compvars.cpp

@@ -340,7 +340,7 @@ static ConcreteCompilerVariable* _call(IREmitter &emitter, llvm::Value* func, vo
 
             // Don't use the IRBuilder since we want to specifically put this in the entry block so it only gets called once.
             // TODO we could take this further and use the same alloca for all function calls?
-            llvm::Instruction* insertion_point = emitter.currentFunction()->func->getEntryBlock().getTerminator();
+            llvm::Instruction* insertion_point = emitter.currentFunction()->func->getEntryBlock().getFirstInsertionPt();
             arg_array = new llvm::AllocaInst(g.llvm_value_type_ptr, n_varargs, "arg_scratch", insertion_point);
         }