Support LOCAL_RENDERSCRIPT_TARGET_API := current

Renderscript was using LOCAL_RENDERSCRIPT_TARGET_API := 0 to mean
current.  Use current instead, and check for it when comparing
if LOCAL_RENDERSCRIPT_TARGET_API >= 21.

Fixes an issue where LOCAL_RENDERSCRIPT_TARGET_API := 0 was being
treated as < 21, causing the renderscript resources to be passed
to aapt2:
out/target/common/obj/APPS/RSTestBackward_intermediates/flat-res/zip_res.flata.contents/raw/bc32: error: resource file cannot be a directory.

Bug: 79481102
Test: m java FORCE_AAPT2=true
Change-Id: I7726d0463ce1693bc9653b4d869ced181c491036
diff --git a/core/package_internal.mk b/core/package_internal.mk
index 18c8f23..62cb4f3 100644
--- a/core/package_internal.mk
+++ b/core/package_internal.mk
@@ -361,7 +361,7 @@
 
 ifeq ($(LOCAL_USE_AAPT2),true)
   my_compiled_res_base_dir := $(intermediates.COMMON)/flat-res
-  ifneq (,$(renderscript_target_api))
+  ifneq (,$(filter-out current,$(renderscript_target_api)))
     ifneq ($(call math_gt_or_eq,$(renderscript_target_api),21),true)
       my_generated_res_zips := $(rs_generated_res_zip)
     endif  # renderscript_target_api < 21