More agressive compiler warnings checker.

Test: Compiled
Change-Id: Icb458772079b0a6743d833a7b6fd8ec3ff5e2ccd
diff --git a/Android.bp b/Android.bp
index 03763d9..4ab57d7 100644
--- a/Android.bp
+++ b/Android.bp
@@ -75,12 +75,16 @@
 
     cflags: [
         "-D_PPD_DEPRECATED=",
+
         "-Wextra",
-        "-Werror",
+        "-Wall",
         "-Wno-unused-parameter",
+        "-Wno-unused-function",
+        "-Wno-unused-variable",
         "-Wno-sign-compare",
         "-Wno-missing-field-initializers",
         "-Wno-implicit-function-declaration",
+        "-Werror",
     ],
 
     export_include_dirs: [