Add a missing ',' in the VNDK variant identicalness check

The invocation of verify-vndk-libs-identical is missing a ',' between
the second and third parameters, in commit
4873e65c8d251a717e5d93025484b35f03ed2fb5.

Change-Id: I88d230db4e6fed5939b1fe9d636d440a00773a41
diff --git a/core/soong_cc_prebuilt.mk b/core/soong_cc_prebuilt.mk
index 8ea1e50..190a7ed 100644
--- a/core/soong_cc_prebuilt.mk
+++ b/core/soong_cc_prebuilt.mk
@@ -130,7 +130,7 @@
   $(same_vndk_variants_stamp): $(my_core_shared_lib) $(LOCAL_PREBUILT_MODULE_FILE)
 		$(call verify-vndk-libs-identical,\
 		    $(PRIVATE_CORE_VARIANT),\
-		    $(PRIVATE_VENDOR_VARIANT)\
+		    $(PRIVATE_VENDOR_VARIANT),\
 		    $(PRIVATE_TOOLS_PREFIX))
 
   $(LOCAL_BUILT_MODULE): $(same_vndk_variants_stamp)