Move gn _run target generation into test().

sandbox/linux/BUILD.gn

Index: sandbox/linux/BUILD.gn
diff --git a/sandbox/linux/BUILD.gn b/sandbox/linux/BUILD.gn
index 341d3639e7368dddaa4aeb37d8abe1fae4e9ba0e..b7d3bfeac8e863e63cb3e56e6de8f9740c51b6b6 100644
--- a/sandbox/linux/BUILD.gn
+++ b/sandbox/linux/BUILD.gn
@@ -192,7 +192,7 @@ action("bpf_dsl_golden") {
       rebase_path(outputs, root_build_dir) + rebase_path(inputs, root_build_dir)
 }
 
-# TODO(GYP): Delete this after we've converted everything to GN.
+# TODO(GYP): Delete these after we've converted everything to GN.
 # The _run targets exist only for compatibility w/ GYP.
 group("sandbox_linux_unittests_run") {
   testonly = true
@@ -201,6 +201,15 @@ group("sandbox_linux_unittests_run") {
   ]
 }
 
+if (is_android) {
+  group("sandbox_linux_unittests_apk_run") {
+    testonly = true
+    deps = [
+      ":sandbox_linux_unittests",
+    ]
+  }
+}
+
 # The main sandboxing test target. "sandbox_linux_unittests" cannot use the
 # test() template because the test is run as an executable not as an APK on
 # Android.