<sys/stat.h>: add lchmod().

Bug: http://b/361334945
Change-Id: I6a76db7bd2f657ad9b058c2672bf7a4e687017f9
diff --git a/libc/libc.map.txt b/libc/libc.map.txt
index 8bb84eb..0d2e42f 100644
--- a/libc/libc.map.txt
+++ b/libc/libc.map.txt
@@ -591,6 +591,7 @@
     killpg;
     klogctl;
     labs;
+    lchmod; # introduced=36
     lchown;
     lcong48; # introduced=23
     ldexp;