Don't support --args inside an --args file

This would let you create a recursive operation filling up the stack
and causing a crash.

Closes: #47
Approved by: cgwalters

bubblewrap.c

@@ -799,7 +799,8 @@ int opt_seccomp_fd = -1;
 
 static void
 parse_args (int *argcp,
-            char ***argvp)
+            char ***argvp,
+            bool in_file)
 {
   SetupOp *op;
   int argc = *argcp;
@@ -828,6 +829,9 @@ parse_args (int *argcp,
           int data_argc;
           int i;
 
+          if (in_file)
+            die ("--args not supported in arguments file");
+
           if (argc < 2)
             die ("--args takes an argument");
 
@@ -866,7 +870,7 @@ parse_args (int *argcp,
             }
 
           data_argv_copy = data_argv; /* Don't change data_argv, we need to free it */
-          parse_args (&data_argc, &data_argv_copy);
+          parse_args (&data_argc, &data_argv_copy, TRUE);
 
           argv += 1;
           argc -= 1;
@@ -1200,7 +1204,7 @@ main (int argc,
   if (argc == 0)
     usage (EXIT_FAILURE);
 
-  parse_args (&argc, &argv);
+  parse_args (&argc, &argv, FALSE);
 
   /* We have to do this if we weren't installed setuid, so let's just DWIM */
   if (!is_privileged)