Add basic support to semihosting (#384) #234

Job	Run time
Check that stm32 generated code is up to date	39s
Unit Test Regz (ubuntu-latest)	17s
Build (ubuntu-latest)	32s
Unit Test Regz (windows-latest)	1m 12s
Build (windows-latest)	1m 32s
Unit Test Regz (macos-latest)	22s
Build (macos-latest)	21s
Build Examples (espressif/esp)	2m 10s
Build Examples (gigadevice/gd32)	2m 14s
Build Website	26s
Build Examples (microchip/avr)	2m 7s
Dry Run Packaging	1m 22s
Build Examples (microchip/atsam)	1m 57s
Build Examples (nordic/nrf5x)	2m 5s
Unit Test Ports (ubuntu-latest, gigadevice/gd32)	16s
Build Examples (nxp/lpc)	2m 3s
Unit Test UF2 (ubuntu-latest)	16s
Unit Test Ports (ubuntu-latest, raspberrypi/rp2xxx)	15s
Build Examples (stmicro/stm32)	27s
Unit Test UF2 (windows-latest)	1m 7s
Unit Test Ports (ubuntu-latest, stmicro/stm32)	27s
Build Examples (raspberrypi/rp2xxx)	2m 26s
Unit Test UF2 (macos-latest)	35s
Unit Test Ports (windows-latest, gigadevice/gd32)	1m 8s
Build Examples (wch/ch32v)	2m 18s
Unit Test Ports (windows-latest, raspberrypi/rp2xxx)	1m 1s
Unit Test Ports (windows-latest, stmicro/stm32)	1m 38s
Unit Test Ports (macos-latest, gigadevice/gd32)	28s
Unit Test Ports (macos-latest, raspberrypi/rp2xxx)	39s
Unit Test Ports (macos-latest, stmicro/stm32)	39s
	32m 59s

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