libinputservice: Enable thread safety annotations

Bug: None
Test: build
Change-Id: I0bb8ac5df1a455c87d4b7a20c9bd0dda759177d4
diff --git a/libs/input/Android.bp b/libs/input/Android.bp
index 55f932d..6c0fd5f 100644
--- a/libs/input/Android.bp
+++ b/libs/input/Android.bp
@@ -55,6 +55,7 @@
         "-Wall",
         "-Wextra",
         "-Werror",
+        "-Wthread-safety",
     ],
 
 }