Add basic support to semihosting #230

Job	Run time
Build Website	19s
Build (ubuntu-latest)	24s
Dry Run Packaging	1m 28s
Build (windows-latest)	1m 52s
Build Examples (espressif/esp)	2m 16s
Check that stm32 generated code is up to date	45s
Build (macos-latest)	24s
Build Examples (gigadevice/gd32)	2m 14s
Unit Test Ports (ubuntu-latest, gigadevice/gd32)	24s
Build Examples (microchip/avr)	2m 11s
Unit Test Ports (ubuntu-latest, raspberrypi/rp2xxx)	21s
Unit Test Regz (ubuntu-latest)	17s
Build Examples (microchip/atsam)	2m 6s
Unit Test Ports (ubuntu-latest, stmicro/stm32)	21s
Unit Test UF2 (ubuntu-latest)	16s
Unit Test Regz (windows-latest)	2m 4s
Build Examples (nordic/nrf5x)	2m 10s
Unit Test Ports (windows-latest, gigadevice/gd32)	1m 47s
Unit Test UF2 (windows-latest)	1m 26s
Unit Test Regz (macos-latest)	26s
Build Examples (nxp/lpc)	1m 58s
Unit Test UF2 (macos-latest)	27s
Unit Test Ports (windows-latest, raspberrypi/rp2xxx)	1m 31s
Build Examples (stmicro/stm32)	19s
Unit Test Ports (windows-latest, stmicro/stm32)	1m 8s
Build Examples (raspberrypi/rp2xxx)	2m 31s
Unit Test Ports (macos-latest, gigadevice/gd32)	25s
Unit Test Ports (macos-latest, raspberrypi/rp2xxx)	42s
Build Examples (wch/ch32v)	2m 20s
Unit Test Ports (macos-latest, stmicro/stm32)	35s
	35m 27s

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