Add fileno_unlocked to support thread sanitizer.

Bug: 25392375
Change-Id: If3f92a0e08a53f4b59e01397e8efa307d8572349
diff --git a/libc/libc.map.txt b/libc/libc.map.txt
index 418d4cf..c378456 100644
--- a/libc/libc.map.txt
+++ b/libc/libc.map.txt
@@ -1337,6 +1337,7 @@
     __pwrite_chk;
     __pwrite64_chk;
     __write_chk;
+    fileno_unlocked;
     getgrgid_r;
     getgrnam_r;
     preadv;