verify_archive_test's must_contain_regex always passes

[krakeusz]

Hey,
The below pseudocode will always pass regardless of the contents of pkg_tar-generated tarball:

load("@rules_pkg//pkg:tar.bzl", "pkg_tar")
load("@rules_pkg//pkg:verify_archive.bzl", "verify_archive_test")

pkg_tar(
    name = "a_tarball",
    srcs = [ ... ],
)

verify_archive_test(
    name = "verify_package_contents",
    must_contain_regex = [
        "anything_really",
    ],
    target = ":a_tarball",
)

Problem is with must_contain_regex implementation. The variable match is undefined and should be matched. A simple typo, apparently not tested.