Pick gnu-libstdc++ based on TARGET_GCC_VERSION

Previously we have only one set of include/lib paths for
LOCAL_NDK_STL_VARIANT:=gnustl_static regardless of GCC
version, which is wrong because each GCC version
come with its own libstdc++.

Change-Id: I2a01c2120b6948aedce00e2f8d08dfc6932126dd
diff --git a/core/binary.mk b/core/binary.mk
index 81dd5bf..5011129 100644
--- a/core/binary.mk
+++ b/core/binary.mk
@@ -60,9 +60,9 @@
     my_ndk_stl_cppflags := -std=c++11
   else
     # LOCAL_NDK_STL_VARIANT is gnustl_static
-    my_ndk_stl_include_path := $(my_ndk_source_root)/cxx-stl/gnu-libstdc++/libs/$(TARGET_$(LOCAL_2ND_ARCH_VAR_PREFIX)CPU_ABI)/include \
-                               $(my_ndk_source_root)/cxx-stl/gnu-libstdc++/include
-    my_ndk_stl_static_lib := $(my_ndk_source_root)/cxx-stl/gnu-libstdc++/libs/$(TARGET_$(LOCAL_2ND_ARCH_VAR_PREFIX)CPU_ABI)/libgnustl_static.a
+    my_ndk_stl_include_path := $(my_ndk_source_root)/cxx-stl/gnu-libstdc++/$($(LOCAL_2ND_ARCH_VAR_PREFIX)TARGET_GCC_VERSION)/libs/$(TARGET_$(LOCAL_2ND_ARCH_VAR_PREFIX)CPU_ABI)/include \
+                               $(my_ndk_source_root)/cxx-stl/gnu-libstdc++/$($(LOCAL_2ND_ARCH_VAR_PREFIX)TARGET_GCC_VERSION)/include
+    my_ndk_stl_static_lib := $(my_ndk_source_root)/cxx-stl/gnu-libstdc++/$($(LOCAL_2ND_ARCH_VAR_PREFIX)TARGET_GCC_VERSION)/libs/$(TARGET_$(LOCAL_2ND_ARCH_VAR_PREFIX)CPU_ABI)/libgnustl_static.a
   endif
   endif
   endif