ANDROID: Incremental fs: Make compatible with existing files

Bug: 166638631
Test: incfs_test passes
Signed-off-by: Paul Lawrence <paullawrence@google.com>
Change-Id: I3b4f61bf881dccd50f05f42326370421945b68db

tools/testing/selftests/filesystems/incfs/utils.c

@@ -314,7 +314,7 @@ int wait_for_pending_reads2(int fd, int timeout_ms,
 	return read_res / sizeof(*prs);
 }
 
-char *concat_file_name(const char *dir, char *file)
+char *concat_file_name(const char *dir, const char *file)
 {
 	char full_name[FILENAME_MAX] = "";