Bazel: Add always pass test to avoid boilerplate in the CI

We don't know whether or not all plugins have test rules, so running a
generic command:

  $ bazelisk test plugins/{name}/...

can lead to no tests found outcome, in which case Bazel will return exit
code 4 that needs to be checked to differentiate from test failure (exit
code 1). To avoid those checks, pass the virtual test that will always
succeed:

  $ bazelisk test //tools/bzl:always_pass_test plugins/{name}/...

See also this upstream issue for this suggested workaround: [1].

[1] https://github.com/bazelbuild/bazel/issues/11465

Change-Id: Ideab64674482400cc48fad55f7ed9f8085909b84
(cherry picked from commit d69773ceb5c84cfcf13749b2f555bf92d22e6f71)
diff --git a/tools/bzl/BUILD b/tools/bzl/BUILD
index a0f5bd1..7febbac 100644
--- a/tools/bzl/BUILD
+++ b/tools/bzl/BUILD
@@ -3,3 +3,8 @@
     "test_empty.sh",
     "test_license.sh",
 ])
+
+sh_test(
+    name = "always_pass_test",
+    srcs = ["always_pass_test.sh"],
+)
diff --git a/tools/bzl/always_pass_test.sh b/tools/bzl/always_pass_test.sh
new file mode 100755
index 0000000..15c58ca
--- /dev/null
+++ b/tools/bzl/always_pass_test.sh
@@ -0,0 +1,21 @@
+#!/bin/sh
+#
+# Copyright (C) 2020 The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# This is a dummy test to put on the command line to avoid no tests
+# found outcome in `bazel test` command. See this upstream issue:
+# https://github.com/bazelbuild/bazel/issues/11465
+
+exit 0