Marlin/buildroot/share/PlatformIO/scripts/common-dependencies-post.py

#
# post:common-dependencies-post.py
# Convenience script to add build flags for Marlin Enabled Features
#
import pioutil
if pioutil.is_pio_build():
	Import("env", "projenv")

	def apply_board_build_flags():
		if not 'BOARD_CUSTOM_BUILD_FLAGS' in env['MARLIN_FEATURES']:
			return
		projenv.Append(CCFLAGS=env['MARLIN_FEATURES']['BOARD_CUSTOM_BUILD_FLAGS'].split())

	# We need to add the board build flags in a post script
	# so the platform build script doesn't overwrite the custom CCFLAGS
	apply_board_build_flags()