message: Better error message when VCPKG_ROOT is independently defined
diff: @@ -143,7 +143,7 @@ static void inner(const VcpkgCmdArguments& args)
  #else
  const int exit_code = chdir(paths.root.c_str());
  #endif
  - Checks::check_exit(VCPKG_LINE_INFO, exit_code == 0, "Changing the working dir failed");
  + Checks::check_exit(VCPKG_LINE_INFO, exit_code == 0, "Changing the working directory to the vcpkg root directory failed. Did you incorrectly define the VCPKG_ROOT environment variable, or did you mistakenly create a file named .vcpkg-root somewhere?");
  if (args.command == "install" || args.command == "remove" || args.command == "export" || args.command == "update")
  {
  