[sysid] Add SysId (#5672)

The source is copied from this commit:
625ff04784.

sysid/src/main/native/cpp/Main.cpp

@@ -0,0 +1,29 @@
+// Copyright (c) FIRST and other WPILib contributors.
+// Open Source Software; you can modify and/or share it under the terms of
+// the WPILib BSD license file in the root directory of this project.
+
+#include <string_view>
+
+#ifndef RUNNING_SYSID_TESTS
+
+void Application(std::string_view saveDir);
+
+#ifdef _WIN32
+int __stdcall WinMain(void* hInstance, void* hPrevInstance, char* pCmdLine,
+                      int nCmdShow) {
+  int argc = __argc;
+  char** argv = __argv;
+#else
+int main(int argc, char** argv) {
+#endif
+  std::string_view saveDir;
+  if (argc == 2) {
+    saveDir = argv[1];
+  }
+
+  Application(saveDir);
+
+  return 0;
+}
+
+#endif