Pass 0 to llvm-rs-cc for current

Apparently empty PRIVATE_RS_TARGET_API is not the same as current,
pass 0 explicitly.

Test: forrest ub-renderscript-test
Change-Id: I8b2001b12161f07c404f78f63a80d82dffa1075f
diff --git a/core/java_renderscript.mk b/core/java_renderscript.mk
index 2d3af0b..d7dd4ed 100644
--- a/core/java_renderscript.mk
+++ b/core/java_renderscript.mk
@@ -75,7 +75,7 @@
 $(rs_generated_src_jar): PRIVATE_RS_FLAGS := $(renderscript_flags)
 $(rs_generated_src_jar): PRIVATE_RS_SOURCE_FILES := $(renderscript_sources_fullpath)
 $(rs_generated_src_jar): PRIVATE_RS_OUTPUT_DIR := $(renderscript_intermediate.COMMON)
-$(rs_generated_src_jar): PRIVATE_RS_TARGET_API := $(filter-out current,$(renderscript_target_api))
+$(rs_generated_src_jar): PRIVATE_RS_TARGET_API := $(patsubst current,0,$(renderscript_target_api))
 $(rs_generated_src_jar): PRIVATE_DEP_FILES := $(bc_dep_files)
 $(rs_generated_src_jar): PRIVATE_RS_OUTPUT_RES_ZIP := $(rs_generated_res_zip)
 $(rs_generated_src_jar): .KATI_IMPLICIT_OUTPUTS := $(rs_generated_res_zip)