remove support for running post lock command

This command was used for example to suspend-to-ram (man page example).

On Linux running this command inherits OOM killer immunity. This could be
abused by an other local user on the same machine (abusing resources).

To keep the use-case for suspend-to-ram an user could write a wrapper script
for it, outside the scope of slock.

Simplify argument handling, because the post-lock command parameter is removed.

Reported by: Acts1631 <acts1631kjv@proton.me>

slock.c

@@ -13,14 +13,12 @@
 #include <stdio.h>
 #include <string.h>
 #include <unistd.h>
-#include <spawn.h>
 #include <sys/types.h>
 #include <X11/extensions/Xrandr.h>
 #include <X11/keysym.h>
 #include <X11/Xlib.h>
 #include <X11/Xutil.h>
 
-#include "arg.h"
 #include "util.h"
 
 char *argv0;
@@ -304,7 +302,7 @@ lockscreen(Display *dpy, struct xrandr *rr, int screen)
 static void
 usage(void)
 {
-	die("usage: slock [-v] [cmd [arg ...]]\n");
+	die("usage: slock [-v]\n");
 }
 
 int
@@ -319,13 +317,12 @@ main(int argc, char **argv) {
 	Display *dpy;
 	int s, nlocks, nscreens;
 
-	ARGBEGIN {
-	case 'v':
+	if (argc > 1 && !strcmp(argv[1], "-v")) {
 		puts("slock-"VERSION);
 		return 0;
-	default:
+	} else if (argc > 1) {
 		usage();
-	} ARGEND
+	}
 
 	/* validate drop-user and -group */
 	errno = 0;
@@ -378,17 +375,6 @@ main(int argc, char **argv) {
 	if (nlocks != nscreens)
 		return 1;
 
-	/* run post-lock command */
-	if (argc > 0) {
-		pid_t pid;
-		extern char **environ;
-		int err = posix_spawnp(&pid, argv[0], NULL, NULL, argv, environ);
-		if (err) {
-			die("slock: failed to execute post-lock command: %s: %s\n",
-			    argv[0], strerror(err));
-		}
-	}
-
 	/* everything is now blank. Wait for the correct password */
 	readpw(dpy, &rr, locks, nscreens, hash);