Use -Werror in external/libcxxabi
am: 3b3514c8d6

Change-Id: I5630e1f672009d433f4bb988e94bea6e388e1976
diff --git a/Android.bp b/Android.bp
index 81877c3..f2a671e 100644
--- a/Android.bp
+++ b/Android.bp
@@ -42,13 +42,15 @@
     include_dirs: ["external/libcxx/include"],
     local_include_dirs:  ["include"],
     export_include_dirs: ["include"],
+    cflags: [
+        "-Wall",
+        "-Werror",
+    ],
     cppflags: [
         "-std=c++14",
         "-fexceptions",
-        "-Wall",
         "-Wextra",
         "-Wno-unused-function",
-        "-Werror",
     ],
     sanitize: {
         never: true,