Mispelled flags are mistaken with file names

[cg-jl]

When mispelling a flag to the compiler, it mistakes it with a file name, which generates a somewhat confusing error message:

$ jakt --cxx-compile-path /opt/bin/clang++-16 test.jakt
Extra unknown argument '/opt/bin/clang++-16', you can only pass one source file (was '--cxx-compile-path')
usage: jakt [cross] [-h] [OPTIONS] <filename>

Perhaps we should assume anything starting with - is an option, so that jakt can complain about non-existing options.
To keep supporting file names that may start with -, we could make use of a marker like -- to signal that flag-like arguments end, so that the next argument is interpreted as a file name, disregarding the - from the start.