[antlir2][image_test] forward args from standalone script

Summary:
In the `buck2 build` version of the test script, forward args from the user to
the underlying test.
This already worked for `buck2 run`, but not the standalone version of the script

Test Plan: testhard

Reviewed By: naveedgol

Differential Revision: D65792011

fbshipit-source-id: 3d1e431c9fb08a466e9fa62c5130a7d6c7faa9f5

antlir/antlir2/testing/image_test.bzl

@@ -82,6 +82,7 @@ def _impl(ctx: AnalysisContext) -> list[Provider]:
             "#!/bin/bash",
             cmd_args(
                 test_cmd,
+                '"$@"',
                 delimiter = " \\\n  ",
             ),
             "\n",