juvix compile: --debug no longer implies -O0 by default

[lukaszcz]

Expected (previous) behaviour: adding --debug without specifying the optimization level implied turning off optimizations. This could be overridden by specifying -O explicitly.

This is no longer the case (even though the command documentation suggests it).

For example

juvix compile native --debug program.juvix

should compile in debug mode without optimizations, i.e., it should be equivalent to

juvix compile native --debug -O0 program.juvix

The command

juvix compile native --debug -O2 program.juvix

should compile in debug mode with optimization level 2.

This can probably be fixed by modifying applyCompileCommonOptions appropriately.