Depend on bzl_library, not on individual bzl files (#244)

tests/BUILD

@@ -56,11 +56,11 @@ sh_test(
     data = [
         ":unittest.bash",
         ":unittest_tests_bzl",
-        "//lib:dicts.bzl",
-        "//lib:new_sets.bzl",
-        "//lib:sets.bzl",
-        "//lib:types.bzl",
-        "//lib:unittest.bzl",
+        "//lib:dicts",
+        "//lib:new_sets",
+        "//lib:sets",
+        "//lib:types",
+        "//lib:unittest",
         "//toolchains/unittest:test_deps",
         "@bazel_tools//tools/bash/runfiles",
     ],