Add OS_PATH_SEPARATOR for platforms which have different path separator characters (e.g. Windows and 'classic' MacOS).

Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/blktrace.c b/blktrace.c
index 297a8a9..1b9bf3b 100644
--- a/blktrace.c
+++ b/blktrace.c
@@ -115,7 +115,7 @@
 		if (!strcmp(dir->d_name, ".") || !strcmp(dir->d_name, ".."))
 			continue;
 
-		sprintf(full_path, "%s/%s", path, dir->d_name);
+		sprintf(full_path, "%s%s%s", path, FIO_OS_PATH_SEPARATOR, dir->d_name);
 		if (lstat(full_path, &st) == -1) {
 			perror("lstat");
 			break;