Fixes: Fix not close trace file when the sim is finished

[juiceRv]

Description

During my testing of LiteX simulations using Verilator, I discovered that when the BIOS executes the finish command to properly terminate the simulation, the FST files were not being closed correctly. This resulted in sim.fst and sim.fst.hier not being merged properly.

Changes

• Fixed the logic to ensure FST files are correctly closed when the finish command is executed.

Testing

• Verified that after executing the finish command, the FST files close correctly and the waveform files merge as expected.

Additional Information

Thank you to the authors for designing such an excellent project with LiteX! I hope this fix can be accepted upstream.

[juiceRv]

litex_sim --cpu-type=picorv32 --sim-debug --gtkwave-savefile --trace --trace-fst --with-sdram --sdram-module MT48LC16M16 --sdram-data-width 32 --soc-csv csr.csv

Once the simulation is running, execute the following trace commands:

trace
sdram_init
trace
finish

[enjoy-digital]

Thanks @juiceRv!