sim: ELF file is deleted after compiling

[xobs]

The build system generates a .hex file that is pulled into the SPI ROM as part of the simulation test bench. However, after this hexfile is generated, it removes the .elf file. In doing so, this makes it more difficult to debug the simulated CPU as it is no longer possible to trace which functions the CPU is executing.

As a workaround, it is possible to remove the .hex file and copy the .elf file out during the build, however this must be done before the build system removes the ELF file.