Don't let the build break!

For some reason, the docs build fails for ag/1124382 - it is probably a
bug in doclava. However, this commit provides a fix that prevents the
build breakage.

Change-Id: Icdead3db345c0b126b4d6d5ff5ca50cf8b4e79b3
diff --git a/v17/leanback/Android.mk b/v17/leanback/Android.mk
index 459d54e..294d7f6 100644
--- a/v17/leanback/Android.mk
+++ b/v17/leanback/Android.mk
@@ -154,7 +154,7 @@
 LOCAL_SRC_FILES := $(leanback.docs.src_files)
 LOCAL_ADDITIONAL_JAVA_DIR := $(gen_res_src_dirs)
 
-LOCAL_SDK_VERSION := 21
+LOCAL_SDK_VERSION := $(SUPPORT_CURRENT_SDK_VERSION)
 LOCAL_IS_HOST_MODULE := false
 LOCAL_DROIDDOC_CUSTOM_TEMPLATE_DIR := build/tools/droiddoc/templates-sdk