Switch to libc++.

gnustl is being removed.

Bug: None
Test: make checkbuild
Change-Id: If41a886c8dcf2abc5aa4e30de4bce58c45cd6387
diff --git a/Android.mk b/Android.mk
index 07c3086..68e62b8 100644
--- a/Android.mk
+++ b/Android.mk
@@ -1051,7 +1051,7 @@
 
 LOCAL_SDK_VERSION := 22
 LOCAL_CPPFLAGS += -Wno-non-virtual-dtor -Wno-delete-non-virtual-dtor
-LOCAL_NDK_STL_VARIANT := gnustl_static
+LOCAL_NDK_STL_VARIANT := c++_static
 LOCAL_RTTI_FLAG := -frtti -fexceptions
 LOCAL_MULTILIB := both
 LOCAL_TIDY_CHECKS := \