Suppress existing warning.

Bug: 66996870
Test: normal build
Exempt-From-Owner-Approval: quick fix broken build
Change-Id: Ifb72429a348ff8e5df42610e77db1ed1171e666d
diff --git a/Android.mk b/Android.mk
index ea0a67f..62451d7 100644
--- a/Android.mk
+++ b/Android.mk
@@ -22,6 +22,7 @@
         -Wall \
         -Werror \
         -Wno-switch \
+        -Wno-unused-function \
         -Wno-unused-parameter \
         -Wno-unused-variable \