the core allows applications to define a app_config.h file, which is automatically included for all source files.
this file can be used to define the same options as build_flags, but allows for more complex configurations.
to use app_config.h, either create a file with that name in the root of your project, or specify a custom path in the platformio.ini file.
[env:hc32f460]
board_build.app_config = src/my_app_config.h
# ...