Assert rather than do bogus things for non-cuda/opencl case.

src/datawizard/memalloc.c

@@ -708,6 +708,8 @@ static size_t _starpu_get_global_mem_size(int dst_node)
 			break;
 		}
 #endif
+		default:
+			STARPU_ASSERT(0);
 	}
 	return global_mem_size;
 }