Check in autogenerated "to_string.cc" files

[GrandChris]

Compiling the project with CMake, Ninja and GCC10 works perfectly fine with not much effort and with no warnings but the linker complains about undefined references to "dwarf::to_string" functions. Trying to manually run the python script fails, probably because of a wrong Python version, which is super annoying. I think it would be better to just check in the generated files to avoid dealing with Python.