Added a hacky build scripts that translates to BeebASM; minor change to 2.3d so the binary would the one I built yesterday and is currently synthesised

Change-Id: I70ad356af1ca7e07c77bbdaaeefbe34bc3dbd007
Added a hardware SPI implementation that's compatible with the PL8 code in SDDOS 2.3

Change-Id: I96c91b305874ba62bcdddb3951ed667583082afc