message: add fallback OTP content
diff: @@ -27,7 +27,7 @@ extern "C" void SystemClock_Config(void); // defined in main.c generated by Cube
  // used during manufacturing to test the struct that will go to the OTP before
  // _actually_ putting anything into OTP. This avoids bulk-destroying STM32's if
  // we introduce unintended breakage in our manufacturing scripts.
  -uint8_t __attribute__((section(".testdata"))) fake_otp[FLASH_OTP_END + 1 - FLASH_OTP_BASE];
  +uint8_t __attribute__((section(".testdata"))) fake_otp[FLASH_OTP_END + 1 - FLASH_OTP_BASE] = {0, 0, 0, HW_VERSION_MAJOR, HW_VERSION_MINOR, HW_VERSION_VOLTAGE};
  Stm32SpiArbiter spi3_arbiter{&hspi3};
  Stm32SpiArbiter& ext_spi_arbiter = spi3_arbiter;
  