Don't use libandroid_support post-21.

Test: m checkbuild
Bug: http://b/119587551
Change-Id: If3a3556ad27e632778efda43da8384a40eedee5a
diff --git a/core/binary.mk b/core/binary.mk
index d7112b6..70f10f9 100644
--- a/core/binary.mk
+++ b/core/binary.mk
@@ -201,7 +201,6 @@
       $(my_ndk_source_root)/cxx-stl/llvm-libc++/include
     my_ndk_stl_include_path += \
       $(my_ndk_source_root)/cxx-stl/llvm-libc++abi/include
-    my_ndk_stl_include_path += $(my_ndk_source_root)/android/support/include
 
     my_libcxx_libdir := \
       $(my_ndk_source_root)/cxx-stl/llvm-libc++/libs/$(my_cpu_variant)
@@ -214,7 +213,13 @@
       my_ndk_stl_shared_lib_fullpath := $(my_libcxx_libdir)/libc++_shared.so
     endif
 
-    my_ndk_stl_static_lib += $(my_libcxx_libdir)/libandroid_support.a
+    ifneq ($(my_ndk_api),current)
+      ifeq ($(call math_lt,$(my_ndk_api),21),true)
+        my_ndk_stl_include_path += $(my_ndk_source_root)/android/support/include
+        my_ndk_stl_static_lib += $(my_libcxx_libdir)/libandroid_support.a
+      endif
+    endif
+
     ifneq (,$(filter armeabi armeabi-v7a,$(my_cpu_variant)))
       my_ndk_stl_static_lib += $(my_libcxx_libdir)/libunwind.a
     endif