Right now using the wrong installer disk image on a board continues with installation.

E.g. it is possible to use the spi-installer.img from libreComputer-amlS805xAc on a pine64-pinebookPro. This particular instance shouldn't cause much harm, but it might be possible to have compatible-enough boards, where it puts the user in a hard situation.

The solution is to, as early as possible, check the target board in the installation script, and bail when it differs from the expectation.