accelsim/gyrosim: fix seg fault if not enough arguments

happens with 'accelsim/gyrosim -R'

src/platforms/posix/drivers/accelsim/accelsim.cpp

@@ -1168,7 +1168,7 @@ accelsim_main(int argc, char *argv[])
 		}
 	}
 
-	if (argc <= 1) {
+	if (myoptind >= argc) {
 		accelsim::usage();
 		return 1;
 	}

src/platforms/posix/drivers/gyrosim/gyrosim.cpp

@@ -1482,6 +1482,11 @@ gyrosim_main(int argc, char *argv[])
 		}
 	}
 
+	if (myoptind >= argc) {
+		gyrosim::usage();
+		return 1;
+	}
+
 	const char *verb = argv[myoptind];
 
 	/*