Add basic support to semihosting #202

Job	Run time
Build Website	22s
Build (ubuntu-latest)	32s
Build Examples (espressif/esp)	2m 14s
Build (windows-latest)	1m 49s
Dry Run Packaging	1m 21s
Build Examples (gigadevice/gd32)	2m 9s
Check that stm32 generated code is up to date	38s
Build (macos-latest)	26s
Build Examples (microchip/avr)	2m 10s
Build Examples (microchip/atsam)	2m 3s
Unit Test Ports (ubuntu-latest, gigadevice/gd32)	19s
Build Examples (nordic/nrf5x)	2m 8s
Unit Test Regz (ubuntu-latest)	17s
Unit Test Ports (ubuntu-latest, raspberrypi/rp2xxx)	25s
Unit Test UF2 (ubuntu-latest)	17s
Build Examples (nxp/lpc)	1m 58s
Unit Test Regz (windows-latest)	1m 44s
Unit Test Ports (ubuntu-latest, stmicro/stm32)	26s
Unit Test UF2 (windows-latest)	59s
Unit Test Regz (macos-latest)	29s
Build Examples (stmicro/stm32)	44s
Unit Test Ports (windows-latest, gigadevice/gd32)	2m 35s
Unit Test UF2 (macos-latest)	29s
Build Examples (raspberrypi/rp2xxx)	2m 22s
Unit Test Ports (windows-latest, raspberrypi/rp2xxx)	1m 31s
Build Examples (wch/ch32v)	2m 15s
Unit Test Ports (windows-latest, stmicro/stm32)	1m 21s
Unit Test Ports (macos-latest, gigadevice/gd32)	33s
Unit Test Ports (macos-latest, raspberrypi/rp2xxx)	42s
Unit Test Ports (macos-latest, stmicro/stm32)	29s
	35m 47s

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