pyosys generator: ignore attributes

[georgerennie]

This allows log_error, log_file_error and log_cmd_error which are all marked [[noreturn]] to be wrapped.

The corresponding diff to the generated c++ is

12653a12654,12671
> 	// WRAPPED from "[[noreturn]] void log_error(const char_p format, ...) YS_ATTRIBUTE(format(printf, 1, 2));" in kernel/log
> 	void log_error(const char * format)
> 	{
> 		::YOSYS_NAMESPACE::log_error("%s", format);
> 	}
> 
> 	// WRAPPED from "[[noreturn]] void log_file_error(const string &filename, int lineno, const char_p format, ...) YS_ATTRIBUTE(format(printf, 3, 4));" in kernel/log
> 	void log_file_error(const string filename, int lineno, const char * format)
> 	{
> 		::YOSYS_NAMESPACE::log_file_error(filename, lineno, "%s", format);
> 	}
> 
> 	// WRAPPED from "[[noreturn]] void log_cmd_error(const char_p format, ...) YS_ATTRIBUTE(format(printf, 1, 2));" in kernel/log
> 	void log_cmd_error(const char * format)
> 	{
> 		::YOSYS_NAMESPACE::log_cmd_error("%s", format);
> 	}
> 
15278a15297,15299
> 		def<void (*)(const char *)>("log_error", YOSYS_PYTHON::log_error);
> 		def<void (*)(const string, int, const char *)>("log_file_error", YOSYS_PYTHON::log_file_error);
> 		def<void (*)(const char *)>("log_cmd_error", YOSYS_PYTHON::log_cmd_error);

Note that although all 3 of these commands are added, log_cmd_error shouldn't be used from python for now as in interactive mode it throws log_cmd_error_exception, expecting the main shell loop to catch it but this exception can't be passed through python so it causes python to throw its own exception. I'm not 100% sure how best to translate this exception so haven't bothered for now