Make sure ESP_PLATFORM is defined when processing CMake files.

tools/cmake/component.cmake

@@ -213,6 +213,7 @@ function(__component_get_requirements)
     __component_write_properties(${component_properties_file})
 
     execute_process(COMMAND "${CMAKE_COMMAND}"
+        -D "ESP_PLATFORM=1"
         -D "BUILD_PROPERTIES_FILE=${build_properties_file}"
         -D "COMPONENT_PROPERTIES_FILE=${component_properties_file}"
         -D "COMPONENT_REQUIRES_FILE=${component_requires_file}"