only run on bzlmod unixy

Author: rickeylev

tests/implicit_namespace_packages/BUILD.bazel

@@ -1,8 +1,10 @@
 load("//python:py_test.bzl", "py_test")
+load("//tests/support:support.bzl", "SUPPORTS_BZLMOD_UNIXY")
 
 py_test(
     name = "namespace_packages_test",
     srcs = ["namespace_packages_test.py"],
+    target_compatible_with = SUPPORTS_BZLMOD_UNIXY,
     deps = [
         "@implicit_namespace_ns_sub1//:pkg",
         "@implicit_namespace_ns_sub2//:pkg",