Set libunwind's STL to none.
am: 9724d2448e

Change-Id: Ie35ba7c5ef643d22cf70c1378a3dd20c98ed65df
diff --git a/Android.bp b/Android.bp
index 538476a..f4653de 100644
--- a/Android.bp
+++ b/Android.bp
@@ -102,6 +102,7 @@
     name: "libunwind",
     defaults: ["libunwind_defaults"],
     sdk_version: "21",
+    stl: "none",
 
     srcs: [
         "src/mi/init.c",