[mlir] Add explicit call to flush

ClangTidy performance suggested to use '\n' instead of std::endl, but it
seems the flushing behavior was intended here (tests started failing).

mlir/include/mlir/ExecutionEngine/RunnerUtils.h

@@ -224,7 +224,7 @@ void printMemRef(const DynamicMemRefType<T> &m) {
                               m.sizes, m.strides);
   if (m.rank == 0)
     std::cout << "]";
-  std::cout << '\n';
+  std::cout << '\n' << std::flush;
 }
 
 template <typename T, int N>