sim: run: support concise env var settings

Support the same syntax as other common utilities where env vars can
be specified before the program to be run without an explicit option.

This behavior can be suppressed by using the -- marker.

sim/common/nrun.c

@@ -229,7 +229,8 @@ main (int argc, char **argv)
 static void
 usage (void)
 {
-  fprintf (stderr, "Usage: %s [options] [--] program [program args]\n", myname);
+  fprintf (stderr, "Usage: %s [options] [VAR=VAL|--] program [program args]\n",
+	   myname);
   fprintf (stderr, "Run `%s --help' for full list of options.\n", myname);
   exit (1);
 }

sim/common/sim-options.c

@@ -719,6 +719,22 @@ sim_parse_args (SIM_DESC sd, char * const *argv)
 	      free (STATE_PROG_FILE (sd));
 	      STATE_PROG_FILE (sd) = NULL;
 
+	      /* Handle any inline variables if -- wasn't used.  */
+	      if (argv[optind] != NULL && optind > 0
+		  && strcmp (argv[optind - 1], "--") != 0)
+		{
+		  while (1)
+		    {
+		      const char *arg = argv[optind];
+
+		      if (strchr (arg, '=') == NULL)
+			break;
+
+		      env_set (sd, arg);
+		      ++optind;
+		    }
+		}
+
 	      new_argv = dupargv (argv + optind);
 	      freeargv (STATE_PROG_ARGV (sd));
 	      STATE_PROG_ARGV (sd) = new_argv;
@@ -914,7 +930,8 @@ void
 sim_print_help (SIM_DESC sd, int is_command)
 {
   if (STATE_OPEN_KIND (sd) == SIM_OPEN_STANDALONE)
-    sim_io_printf (sd, "Usage: %s [options] [--] program [program args]\n",
+    sim_io_printf (sd,
+		   "Usage: %s [options] [VAR=VAL|--] program [program args]\n",
 		   STATE_MY_NAME (sd));
 
   /* Initialize duplicate argument checker.  */
@@ -950,6 +967,9 @@ sim_print_help (SIM_DESC sd, int is_command)
   if (STATE_OPEN_KIND (sd) == SIM_OPEN_STANDALONE)
     {
       sim_io_printf (sd, "\n");
+      sim_io_printf (sd,
+		     "VAR=VAL         Environment variables to set.  "
+		     "Ignored if -- is used.\n");
       sim_io_printf (sd, "program args    Arguments to pass to simulated program.\n");
       sim_io_printf (sd, "                Note: Very few simulators support this.\n");
     }