Shove kicad2step into pcbnew itself with a new cli

thirdparty/argparse/samples/required_optional_argument.cpp

@@ -0,0 +1,19 @@
+#include <argparse/argparse.hpp>
+
+int main(int argc, char *argv[]) {
+  argparse::ArgumentParser program("test");
+
+  program.add_argument("-o", "--output")
+      .required()
+      .help("specify the output file.");
+
+  try {
+    program.parse_args(argc, argv);
+  } catch (const std::runtime_error &err) {
+    std::cerr << err.what() << std::endl;
+    std::cerr << program;
+    std::exit(1);
+  }
+
+  std::cout << "Output written to " << program.get("-o") << "\n";
+}