Use -Werror in frameworks/base

* Fix unused variable and return value warnings.

Bug: 66996870
Test: build with WITH_TIDY=1
Change-Id: I890e65a20848d00559ba5a4f9691be1347b456af
diff --git a/tools/bit/Android.bp b/tools/bit/Android.bp
index 258e9b5..a806271 100644
--- a/tools/bit/Android.bp
+++ b/tools/bit/Android.bp
@@ -30,6 +30,11 @@
         "util.cpp",
     ],
 
+    cflags: [
+        "-Wall",
+        "-Werror",
+    ],
+
     static_libs: [
         "libexpat",
         "libinstrumentation",