Build with -Wall and -Werror.

Test: pass
Change-Id: I0b14bfca491b67883bdff079b2e863db4691b635
diff --git a/Android.bp b/Android.bp
index d44a5e7..59edb20 100644
--- a/Android.bp
+++ b/Android.bp
@@ -18,6 +18,11 @@
     "transport",      // libhidltransport
 ]
 
+libhidl_flags = [
+    "-Wall",
+    "-Werror",
+]
+
 cc_test {
     name: "libhidl_test",
     gtest: false,
@@ -37,5 +42,5 @@
     cflags: [
         "-O0",
         "-g",
-    ],
+    ] + libhidl_flags,
 }