Integrating CubeMX USB (USB_DEVICE, Middleware) into PlatformIO project

“It looks like it worked this way.”

[platformio]
src_dir = .

[env:genericSTM32F103C8]
platform = ststm32
board = genericSTM32F103C8
framework = stm32cube
upload_protocol = stlink
debug_tool = stlink

build_flags =
  -I Core/Inc
  -I Drivers/CMSIS/Device/ST/STM32F1xx/Include
  -I Drivers/CMSIS/Include
  -I USB_DEVICE/App
  -I USB_DEVICE/Target
  -I Middlewares/ST/STM32_USB_Device_Library/Core/Inc
  -I Middlewares/ST/STM32_USB_Device_Library/Class/CDC/Inc
  -D USE_HAL_DRIVER
  -D HSE_VALUE=8000000U

build_src_filter =
  +<Core/Src/*.c>
  -<Core/Src/system_stm32f1xx.c>               
  +<USB_DEVICE/App/*.c>
  +<USB_DEVICE/Target/*.c>
  +<Middlewares/ST/STM32_USB_Device_Library/Core/Src/*.c>
  +<Middlewares/ST/STM32_USB_Device_Library/Class/CDC/Src/*.c>
  -<Core/Startup/*>