Update platform CMake to include greentea test dir

Author: rajkan01

platform/CMakeLists.txt

@@ -3,7 +3,7 @@
 
 if(CMAKE_PROJECT_NAME STREQUAL PROJECT_NAME AND BUILD_TESTING)
     if(BUILD_GREENTEA_TESTS)
-        # add greentea test
+        add_subdirectory(tests/TESTS)
     else()
         add_subdirectory(tests/UNITTESTS)
     endif()

platform/tests/TESTS/CMakeLists.txt

@@ -0,0 +1,27 @@
+# Copyright (c) 2021 ARM Limited. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+
+add_subdirectory(mbed_functional/callback)
+add_subdirectory(mbed_functional/callback_big)
+add_subdirectory(mbed_functional/callback_small)
+add_subdirectory(mbed_micro/attributes)
+add_subdirectory(mbed_micro/call_before_main)
+add_subdirectory(mbed_micro/cpp)
+add_subdirectory(mbed_micro/div)
+add_subdirectory(mbed_micro/static_assert)
+add_subdirectory(mbed_platform/atomic)
+add_subdirectory(mbed_platform/CircularBuffer)
+add_subdirectory(mbed_platform/crash_reporting)
+add_subdirectory(mbed_platform/error_handling)
+add_subdirectory(mbed_platform/FileHandle)
+add_subdirectory(mbed_platform/minimal-printf/compliance)
+add_subdirectory(mbed_platform/SharedPtr)
+add_subdirectory(mbed_platform/SingletonPtr)
+add_subdirectory(mbed_platform/Stream)
+add_subdirectory(mbed_platform/system_reset)
+add_subdirectory(mbed_platform/Transaction)
+add_subdirectory(mbed_platform/wait_ns)
+add_subdirectory(mbed_platform/stats_cpu)
+add_subdirectory(mbed_platform/stats_heap)
+add_subdirectory(mbed_platform/stats_sys)
+add_subdirectory(mbed_platform/stats_thread)