This commit includes freertos/event_groups.h header and removes the
forward declaration for EventGroupHandle_t.
Signed-off-by: Sudeep Mohanty <sudeep.mohanty@espressif.com>
Older CMake (< 3.8, but still supported in IDF) doesn't support target_compile_features() for cxx_std_17.
If CMake doesn't know C++17 features, set it manually via comile options.