Fix strangeness with bootloader build not picking up latest changes. This was due to the target files being put in `..\build\target\bootloader\prod-4\..\bootloader\src\...` - notice the parent directory ref in the middle. This means outputs for different products end up in the same directory, because the bootloader module path wasn't overridden as '.'. After this fix, the object files are put in `..\build\target\bootloader\prod-4\.\src'