Add libz to static libs of libutils_test

libz is no longer statically linked into libunwindstatck, so needs to be
added explicitly to the static libs of this test

Bug: 281077552
Test: presubmits
Change-Id: Ia04b63cb8dfd5e80536a188a35d036dd3e4fd775
diff --git a/libutils/Android.bp b/libutils/Android.bp
index ad5b752..e22c909 100644
--- a/libutils/Android.bp
+++ b/libutils/Android.bp
@@ -366,6 +366,7 @@
                 "libunwindstack_no_dex",
                 "libutils",
                 "libutilscallstack",
+                "libz",
             ],
         },
     },