Support `atest update_engine_unittests`.

We need a few changes to the building rules to support running the test
with atest. In particular, we need a customized test config to filter
out the helper executables. The change doesn't affect the traditionally
way of running tests with `adb sync data` + `adb shell
/d/n/u/update_engine_unittests`.

This is one of the prerequisites to run update_engine_unittests with
TEST_MAPPING [1]. It still requires additional works to enable the test
in pre/post-submit though (currently it's failing on GCE devices due to
missing shared libraries).

[1] https://source.android.com/compatibility/tests/development/test-mapping

Fixes: 131438455
Test: `atest update_engine_unittests` on blueline.
Test: TreeHugger; check that the existing GCL config'd test keeps working.
Change-Id: If602d69d84e0d926c579324d988c94b57240b113
diff --git a/Android.bp b/Android.bp
index ce43bea..9e8296b 100644
--- a/Android.bp
+++ b/Android.bp
@@ -550,8 +550,6 @@
 
     gtest: false,
     stem: "delta_generator",
-    relative_install_path: "update_engine_unittests",
-    no_named_install_directory: true,
 }
 
 // test_http_server (type: executable)
@@ -566,8 +564,6 @@
     ],
 
     gtest: false,
-    relative_install_path: "update_engine_unittests",
-    no_named_install_directory: true,
 }
 
 // test_subprocess (type: executable)
@@ -579,8 +575,6 @@
     srcs: ["test_subprocess.cc"],
 
     gtest: false,
-    relative_install_path: "update_engine_unittests",
-    no_named_install_directory: true,
 }
 
 // Public keys for unittests.
@@ -628,11 +622,6 @@
         "libpayload_generator_exports",
         "libupdate_engine_android_exports",
     ],
-    required: [
-        "test_http_server",
-        "test_subprocess",
-        "ue_unittest_delta_generator",
-    ],
 
     static_libs: [
         "libpayload_generator",
@@ -646,6 +635,9 @@
     ],
 
     data: [
+        ":test_http_server",
+        ":test_subprocess",
+        ":ue_unittest_delta_generator",
         ":ue_unittest_disk_imgs",
         ":ue_unittest_keys",
         "unittest_key.pem",
@@ -654,6 +646,11 @@
         "update_engine.conf",
     ],
 
+    // We cannot use the default generated AndroidTest.xml because of the use of helper modules
+    // (i.e. test_http_server, test_subprocess, ue_unittest_delta_generator).
+    test_config: "test_config.xml",
+    test_suites: ["device-tests"],
+
     srcs: [
         "boot_control_android_unittest.cc",
         "certificate_checker_unittest.cc",