Provide LOCAL_RENDERSCRIPT_TARGET_API override.

BUG=5206223

This allows us to set the RS API level independent of the other SDK
versions that a developer might choose.

Change-Id: Id8b476abcbbbdaa86e04ba0ea16414cb2fa5bd15
diff --git a/core/clear_vars.mk b/core/clear_vars.mk
index 1b9bb8a..c5e4cc7 100644
--- a/core/clear_vars.mk
+++ b/core/clear_vars.mk
@@ -106,6 +106,7 @@
 LOCAL_RENDERSCRIPT_INCLUDES:=
 LOCAL_RENDERSCRIPT_INCLUDES_OVERRIDE:=
 LOCAL_RENDERSCRIPT_CC:=
+LOCAL_RENDERSCRIPT_TARGET_API:=
 LOCAL_BUILD_HOST_DEX:=
 LOCAL_DEX_PREOPT:=
 LOCAL_PROTOC_OPTIMIZE_TYPE:= # lite(default),micro,full