Use -Werror in bionic

Bug: 66996870
Test: build with WITH_TIDY=1
Change-Id: Ic68141a5c50880c485646e38349f94b866267bd9
diff --git a/tools/relocation_packer/Android.bp b/tools/relocation_packer/Android.bp
index 2907b31..cd6053a 100644
--- a/tools/relocation_packer/Android.bp
+++ b/tools/relocation_packer/Android.bp
@@ -16,11 +16,13 @@
 
 cc_defaults {
     name: "relocation_packer_flags",
-    cppflags: [
+    cflags: [
         "-Wall",
+        "-Werror",
+    ],
+    cppflags: [
         "-Wextra",
         "-Wunused",
-        "-Werror",
         "-Wold-style-cast",
     ],