Build the libc++ variant of libbacktrace on the host for Mac.

Bug: 13751317
Change-Id: Iefadec1cd9b3ca109ac436bd5eb7c096c2dcbe40
diff --git a/libbacktrace/Android.mk b/libbacktrace/Android.mk
index 5a0bc7f..74bae1a 100755
--- a/libbacktrace/Android.mk
+++ b/libbacktrace/Android.mk
@@ -186,4 +186,21 @@
 
 include $(BUILD_HOST_SHARED_LIBRARY)
 
+# Don't build for unbundled branches
+ifeq (,$(TARGET_BUILD_APPS))
+#-------------------------------------------------------------------------
+# The libbacktrace library (libc++)
+#-------------------------------------------------------------------------
+include $(CLEAR_VARS)
+
+LOCAL_MODULE := libbacktrace_libc++
+LOCAL_MODULE_TAGS := optional
+
+LOCAL_SRC_FILES := \
+	BacktraceMap.cpp \
+
+include $(BUILD_HOST_SHARED_LIBRARY)
+
+endif # TARGET_BUILD_APPS
+
 endif # HOST_OS-darwin