create a new struct action_node
typedef struct action_node {
    char **args;  // An array of strings suitable to be passed to execvp
    struct action_node *next_act;
} Action;


/* Create a new action node.
 * Return a pointer to this action node.
 */
Action *create_action_node(char **args){
    Action *new_action_node = malloc(sizeof(Action));
    return new_action_node;
}