pledge in doas. startup pledge "stdio rpath getpw proc exec id". 4

pledge in doas.  startup pledge "stdio rpath getpw proc exec id".  4
more times after that more attributes are dropped: "proc" after bsd
auth has spawned/received result from the login_* program; "getpw"
after the final getpwent lookup, "id" after the final uid changing,
and "rpath" after constructing getcwd.  leaving only "exec", for the
ride into execve().