Add support for MKS Robin board (#12650)

Implement initial support for MKS Robin (STM32F103ZET6) board.
Custom build script is used to generate encrypted firmware compatible with original MSK Robin bootloader (i.e. safe firmware update from SD card and possibility to go back to original close-source firmware).

platformio.ini

@@ -293,6 +293,26 @@ lib_ignore    = Adafruit NeoPixel, c1921b4
 src_filter    = ${common.default_src_filter} +<src/HAL/HAL_STM32F4>
 monitor_speed = 250000
 
+#
+# MKS Robin (STM32F103ZET6)
+#
+[env:mks_robin]
+platform      = ststm32
+framework     = arduino
+board         = genericSTM32F103ZE
+extra_scripts = buildroot/share/PlatformIO/scripts/mks_robin.py
+build_flags   = !python Marlin/src/HAL/HAL_STM32F1/stm32f1_flag_script.py
+  ${common.build_flags}
+src_filter    = ${common.default_src_filter} +<src/HAL/HAL_STM32F1>
+lib_deps      = ${common.lib_deps}
+lib_ignore    = c1921b4
+  libf3c
+  lib066
+  Adafruit NeoPixel_ID28
+  Adafruit NeoPixel
+  libf3e
+  TMC26XStepper
+
 #
 # Teensy 3.5 / 3.6 (ARM Cortex-M4)
 #