allow command line argument order used by mount(8)

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

@@ -512,9 +512,17 @@ static int fuse_exfat_main(char* mount_options, char* mount_point)
 			&fuse_exfat_ops, NULL);
 }
 
+static void read_arg(char **param, int *argc, char ***argv) {
+	if (!*param && *argc > optind && (*argv)[optind][0] != '-') {
+		*param = (*argv)[optind];
+		((*argv)++)[1] = (*argv)[0];
+		(*argc)--;
+	}
+}
+
 int main(int argc, char* argv[])
 {
-	const char* spec = NULL;
+	char* spec = NULL;
 	char* mount_point = NULL;
 	char* fuse_options;
 	char* exfat_options;
@@ -523,6 +531,9 @@ int main(int argc, char* argv[])
 
 	printf("FUSE exfat %s\n", VERSION);
 
+	read_arg(&spec, &argc, &argv);
+	read_arg(&mount_point, &argc, &argv);
+
 	fuse_options = strdup("allow_other,"
 #if defined(__linux__) || defined(__FreeBSD__)
 			"big_writes,"
@@ -573,15 +584,16 @@ int main(int argc, char* argv[])
 			usage(argv[0]);
 			break;
 		}
+
+		read_arg(&spec, &argc, &argv);
+		read_arg(&mount_point, &argc, &argv);
 	}
-	if (argc - optind != 2)
+	if (!mount_point || 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)
 	{