external: import cpu_features library

Taken from https://github.com/google/cpu_features at revision
26133d3b620c2c27f31d571efd27371100f891e9

external/cpu_features/test/hwcaps_for_testing.h

@@ -0,0 +1,27 @@
+// Copyright 2017 Google Inc.
+//
+// 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.
+
+#ifndef CPU_FEATURES_TEST_HWCAPS_FOR_TESTING_H_
+#define CPU_FEATURES_TEST_HWCAPS_FOR_TESTING_H_
+
+#include "internal/hwcaps.h"
+
+namespace cpu_features {
+
+void SetHardwareCapabilities(uint32_t hwcaps, uint32_t hwcaps2);
+void SetPlatformTypes(const char *platform, const char *base_platform);
+
+}  // namespace cpu_features
+
+#endif  // CPU_FEATURES_TEST_HWCAPS_FOR_TESTING_H_