Add API 24 to reference selector.

Change-Id: I153245ef814e27bf50f9d972ad1aa34fd92e6b8a
diff --git a/Android.mk b/Android.mk
index 76e9b33..795878b 100644
--- a/Android.mk
+++ b/Android.mk
@@ -847,7 +847,7 @@
     -since $(SRC_API_DIR)/21.txt 21 \
     -since $(SRC_API_DIR)/22.txt 22 \
     -since $(SRC_API_DIR)/23.txt 23 \
-    -since ./frameworks/base/api/current.txt N \
+    -since $(SRC_API_DIR)/24.txt 24 \
 		-werror -hide 111 -hide 113 \
 		-overview $(LOCAL_PATH)/core/java/overview.html