mark zipalign_test as unit tests

Test: make
Bug: 175408655
Change-Id: I03a7a0bb19ea408830acbf1ebe12ffb25012af91
diff --git a/tools/zipalign/Android.bp b/tools/zipalign/Android.bp
index 135cd76..1ebf4eb 100644
--- a/tools/zipalign/Android.bp
+++ b/tools/zipalign/Android.bp
@@ -57,6 +57,9 @@
     srcs: [
         "tests/src/*_test.cpp",
     ],
+    test_options: {
+        unit_test: true,
+    },
     static_libs: [
         "libbase",
         "libzipalign",