ANDROID: Kleaf: Add build test for unsafe DDK headers

* The current issue is that unsafe headers is a target build on demand
  when the `allow_ddk_unsafe_headers` flag is set, for this reason this
  test uses a transition to force that flag to be set.

* This introduces a new Bazel sub-package bazel/test which could be used
  later for more tests if needed.

Tested: tools/bazel test //common/bazel/test
Bug: 325638347
Change-Id: I47236bb625e5d114c0c383035b0e4da809b0ff31
Signed-off-by: Ulises Mendez Martinez <umendez@google.com>

bazel/test/BUILD.bazel

@@ -0,0 +1,15 @@
+# SPDX-License-Identifier: GPL-2.0 OR Apache-2.0
+# Copyright (C) 2026 The Android Open Source Project
+
+load(":kleaf_test.bzl", "ddk_headers_build_test")
+
+ddk_headers_build_test(
+    name = "ddk_headers_build_test",
+)
+
+test_suite(
+    name = "test",
+    tests = [
+        ":ddk_headers_build_test",
+    ],
+)

bazel/test/kleaf_test.bzl

@@ -0,0 +1,58 @@
+# SPDX-License-Identifier: GPL-2.0 OR Apache-2.0
+# Copyright (C) 2026 The Android Open Source Project
+
+"""Tests on Kleaf using ACK / GKI as a baseline."""
+
+load("@bazel_skylib//rules:build_test.bzl", "build_test")
+
+_ALLOW_DDK_UNSAFE_HEADERS_SETTING = "//build/kernel/kleaf:allow_ddk_unsafe_headers"
+
+def _ddk_unsafe_headers_transition_impl(_settings, _attr):
+    return {_ALLOW_DDK_UNSAFE_HEADERS_SETTING: True}
+
+_ddk_unsafe_headers_transition = transition(
+    implementation = _ddk_unsafe_headers_transition_impl,
+    inputs = [],
+    outputs = [_ALLOW_DDK_UNSAFE_HEADERS_SETTING],
+)
+
+# This is a simple wrapper to trigger the transition to add unsafe headers.
+def _ddk_headers_wrapper_impl(ctx):
+    return ctx.attr.target[DefaultInfo]
+
+_ddk_headers_wrapper = rule(
+    implementation = _ddk_headers_wrapper_impl,
+    # test = True,
+    attrs = {
+        "target": attr.label(
+            cfg = "exec",
+        ),
+        "_allowlist_function_transition": attr.label(
+            default = "@bazel_tools//tools/allowlists/function_transition_allowlist",
+        ),
+    },
+    cfg = _ddk_unsafe_headers_transition,
+)
+
+def ddk_headers_build_test(
+        name,
+        **kwargs):
+    """Define a test to check DDK headers build correctly.
+
+    Args:
+        name: Name of the test
+        **kwargs: additional kwargs common to all rules.
+    """
+
+    _ddk_headers_wrapper(
+        name = name + "_ddk_headers_wrapped",
+        target = "//common:all_headers",
+    )
+
+    build_test(
+        name = name,
+        targets = [
+            name + "_ddk_headers_wrapped",
+        ],
+        **kwargs
+    )