fix command line argument order

The mount spec and directory are passed as the first and second
arguments to the helper, followed by the options.

The current implementation works on glibc but fails on POSIX-conforming
C libraries such as musl.

fuse/main.c

@@ -359,7 +359,7 @@ static void fuse_exfat_destroy(void* unused)
 
 static void usage(const char* prog)
 {
-	fprintf(stderr, "Usage: %s [-d] [-o options] [-V] <device> <dir>\n", prog);
+	fprintf(stderr, "Usage: %s <device> <dir> [-d] [-o options] [-V]\n", prog);
 	exit(1);
 }
 
@@ -523,6 +523,13 @@ int main(int argc, char* argv[])
 
 	printf("FUSE exfat %s\n", VERSION);
 
+	if (argc < 3) usage(argv[0]);
+	spec = argv[1];
+	mount_point = argv[2];
+	argv[2] = argv[0];
+	argc -= 2;
+	argv += 2;
+
 	fuse_options = strdup("allow_other,"
 #if defined(__linux__) || defined(__FreeBSD__)
 			"big_writes,"
@@ -574,14 +581,12 @@ int main(int argc, char* argv[])
 			break;
 		}
 	}
-	if (argc - optind != 2)
+	if (argc > optind)
 	{
 		free(exfat_options);
 		free(fuse_options);
 		usage(argv[0]);
 	}
-	spec = argv[optind];
-	mount_point = argv[optind + 1];
 
 	if (exfat_mount(&ef, spec, exfat_options) != 0)
 	{