Dependency Ordering Fix

[rhapsodyv]

Description

When using TMC 2209 Uart, the lib TMCStepper depends on SoftwareSerialM (feature: HAS_TMC_SW_SERIAL). The problem is that no matter the way we send the dependencies to platformio lib_deps, it randomly send to the link the libs in the wrong order.

The linker needs: dependent first, dependency last. Because as it is compiling, it discards non used references (until the compiled file). So, if SoftwareSerialM appear before TMCStepper in the linker command line, all symbols in SoftwareSerialM will be discarded, because they aren't used yet. The correct order is: TMCStepper first, SoftwareSerialM last.

Both dependency graph puts the SoftwareSerialM before TMCStepper....

Dependency Graph
|-- <lvgl> 6.1.1
|-- <SoftwareSerialM> 1.0.0
|-- <TMCStepper> 0.7.1
|   |-- <SoftwareSerialM> 1.0.0
|-- <STM32ADC> 1.0
|-- <EEPROM>
|-- <USBComposite for STM32F1> 0.91
|-- <Wire> 1.0
|-- <FreeRTOS701>
|-- <Servo(STM32F1)> 1.1.2

Or

Dependency Graph
|-- <lvgl> 6.1.1
|-- <TMCStepper> 0.7.1
|   |-- <SoftwareSerialM> 1.0.0
|-- <SoftwareSerialM> 1.0.0
|-- <STM32ADC> 1.0
|-- <EEPROM>
|-- <USBComposite for STM32F1> 0.91
|-- <Wire> 1.0
|-- <FreeRTOS701>
|-- <Servo(STM32F1)> 1.1.2

This PR add a linker flag (-Wl,--start-group), to solve it.

Benefits

• Fix dependency ordering issue
• We won't be any more link ordering problem

Related Issues

#18699

[rhapsodyv]

Closed until I get a better understanding of how SoftwareSerialM and SoftwareSerial are used.