Fix a linker error: undefined kMaxSmallSize (#2476)

When building with a recent version of xt-clang and -std=c++11, the linker errs on missing definition of a static constexpr class member. In C++11, static class members still had to be defined in a C++11 file and TFLM code is expected to be compatible with C++11.

BUG=323856831

tensorflow/lite/kernels/internal/runtime_shape.cc

diff --git a/tensorflow/lite/kernels/internal/runtime_shape.cc b/tensorflow/lite/kernels/internal/runtime_shape.cc
new file mode 100644
index 0000000..dd12278
--- /dev/null
+++ b/tensorflow/lite/kernels/internal/runtime_shape.cc
@@ -0,0 +1,23 @@
+/* Copyright 2023 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+
+#include "tensorflow/lite/kernels/internal/runtime_shape.h"
+
+namespace tflite {
+
+// Defining a constexpr static class member is necessary in C++11
+constexpr int tflite::RuntimeShape::kMaxSmallSize;
+
+}  // namespace tflite