STiROT_iLoader: bugs in prebuild.bat

[Steve Melnikoff]

In STM32Cube_FW_H7RS_V1.3.0, file Projects/STM32H7S78-DK/Applications/ROT/STiROT_iLoader/STM32CubeIDE/prebuild.bat:

As currently written, it fails in a couple of places. Here are the changes necessary for it to run:

(The system won't let me upload the edited batch file.)