Move libz vndk-sp from ll-ndk

The ABI of libz is not as stable as it is for ll-ndk.

Bug: 37617391
Test: build and boot
Change-Id: Ieff0af0c70fc2496db96c7b0323ae096add64658
diff --git a/vndk/vndk-sp-libs.mk b/vndk/vndk-sp-libs.mk
index 6b405e8..e3dab54 100644
--- a/vndk/vndk-sp-libs.mk
+++ b/vndk/vndk-sp-libs.mk
@@ -28,5 +28,6 @@
     libhidlbase \
     libhidlmemory \
     libhidltransport \
+    libz \
 
 endif