Need help with building Marline 2.0 for cr10 w/ MKS Robin E3

[MrUNOwen]

I'm getting the following error when building Marline 2.0 for MKS Robin E3:

 Compiling .pio/build/mks_robin_e3/src/src/HAL/STM32F1/msc_sd.cpp.o
In file included from Marlin/src/HAL/STM32F1/../../inc/../HAL/HAL.h:26:0,
                 from Marlin/src/HAL/STM32F1/../../inc/MarlinConfig.h:31,
                 from Marlin/src/HAL/STM32F1/MarlinSerial.cpp:25:
Marlin/src/HAL/STM32F1/../../inc/../HAL/./STM32F1/HAL.h:85:4: error: #error "SERIAL_PORT must be -1 or from 1 to 5. Please update your configuration."
   #error "SERIAL_PORT must be -1 or from 1 to 5. Please update your configuration."
    ^~~~~
In file included from Marlin/src/HAL/STM32F1/../../inc/../HAL/HAL.h:26:0,
                 from Marlin/src/HAL/STM32F1/../../inc/MarlinConfig.h:31,
                 from Marlin/src/HAL/STM32F1/HAL_SPI.cpp:32:
Marlin/src/HAL/STM32F1/../../inc/../HAL/./STM32F1/HAL.h:85:4: error: #error "SERIAL_PORT must be -1 or from 1 to 5. Please update your configuration."
   #error "SERIAL_PORT must be -1 or from 1 to 5. Please update your configuration."
    ^~~~~
Compiling .pio/build/mks_robin_e3/src/src/HAL/STM32F1/onboard_sd.cpp.o
In file included from Marlin/src/HAL/STM32F1/../../inc/../HAL/HAL.h:26:0,
                 from Marlin/src/HAL/STM32F1/../../inc/MarlinConfig.h:31,
                 from Marlin/src/HAL/STM32F1/HAL.cpp:30:
Marlin/src/HAL/STM32F1/../../inc/../HAL/./STM32F1/HAL.h:85:4: error: #error "SERIAL_PORT must be -1 or from 1 to 5. Please update your configuration."
   #error "SERIAL_PORT must be -1 or from 1 to 5. Please update your configuration."
    ^~~~~
In file included from Marlin/src/HAL/STM32F1/../../inc/../HAL/HAL.h:26:0,
                 from Marlin/src/HAL/STM32F1/../../inc/MarlinConfig.h:31,
                 from Marlin/src/HAL/STM32F1/SPI.cpp:43:
Marlin/src/HAL/STM32F1/../../inc/../HAL/./STM32F1/HAL.h:85:4: error: #error "SERIAL_PORT must be -1 or from 1 to 5. Please update your configuration."
   #error "SERIAL_PORT must be -1 or from 1 to 5. Please update your configuration."
    ^~~~~
In file included from Marlin/src/HAL/STM32F1/../../inc/../HAL/HAL.h:26:0,
                 from Marlin/src/HAL/STM32F1/../../inc/MarlinConfig.h:31,
                 from Marlin/src/HAL/STM32F1/eeprom_bl24cxx.cpp:30:
Marlin/src/HAL/STM32F1/../../inc/../HAL/./STM32F1/HAL.h:85:4: error: #error "SERIAL_PORT must be -1 or from 1 to 5. Please update your configuration."
   #error "SERIAL_PORT must be -1 or from 1 to 5. Please update your configuration."
    ^~~~~
In file included from Marlin/src/HAL/STM32F1/dogm/../../../inc/../HAL/HAL.h:26:0,
                 from Marlin/src/HAL/STM32F1/dogm/../../../inc/MarlinConfig.h:31,
                 from Marlin/src/HAL/STM32F1/dogm/u8g_com_stm32duino_swspi.cpp:21:
Marlin/src/HAL/STM32F1/dogm/../../../inc/../HAL/./STM32F1/HAL.h:85:4: error: #error "SERIAL_PORT must be -1 or from 1 to 5. Please update your configuration."
   #error "SERIAL_PORT must be -1 or from 1 to 5. Please update your configuration."
    ^~~~~
In file included from Marlin/src/HAL/STM32F1/../../inc/../HAL/HAL.h:26:0,
                 from Marlin/src/HAL/STM32F1/../../inc/MarlinConfig.h:31,
                 from Marlin/src/HAL/STM32F1/Servo.cpp:25:
Marlin/src/HAL/STM32F1/../../inc/../HAL/./STM32F1/HAL.h:85:4: error: #error "SERIAL_PORT must be -1 or from 1 to 5. Please update your configuration."
   #error "SERIAL_PORT must be -1 or from 1 to 5. Please update your configuration."
    ^~~~~
*** [.pio/build/mks_robin_e3/src/src/HAL/STM32F1/MarlinSerial.cpp.o] Error 1
*** [.pio/build/mks_robin_e3/src/src/HAL/STM32F1/HAL_SPI.cpp.o] Error 1
In file included from Marlin/src/HAL/STM32F1/../../inc/../HAL/HAL.h:26:0,
                 from Marlin/src/HAL/STM32F1/../../inc/MarlinConfig.h:31,
                 from Marlin/src/HAL/STM32F1/eeprom_if_iic.cpp:30:
Marlin/src/HAL/STM32F1/../../inc/../HAL/./STM32F1/HAL.h:85:4: error: #error "SERIAL_PORT must be -1 or from 1 to 5. Please update your configuration."
   #error "SERIAL_PORT must be -1 or from 1 to 5. Please update your configuration."
    ^~~~~
*** [.pio/build/mks_robin_e3/src/src/HAL/STM32F1/HAL.cpp.o] Error 1
In file included from Marlin/src/HAL/STM32F1/../../inc/../HAL/HAL.h:26:0,
                 from Marlin/src/HAL/STM32F1/../../inc/MarlinConfig.h:31,
                 from Marlin/src/HAL/STM32F1/eeprom_flash.cpp:32:
Marlin/src/HAL/STM32F1/../../inc/../HAL/./STM32F1/HAL.h:85:4: error: #error "SERIAL_PORT must be -1 or from 1 to 5. Please update your configuration."
   #error "SERIAL_PORT must be -1 or from 1 to 5. Please update your configuration."

Normally specifying the board type usually addresses these kinds of configureations. Any Advice?

#defineMOTHERBOARDBOARD_MKS_ROBIN_E3