pkg_tar with "include_runfiles = True" includes _main/app.exe in tarfile (exe is included twice)

I have the following pkt_tar in BUILD.bazel

```
pkg_tar(
    name = "tarfile",
    srcs = [
        ":openroad",
    ],
    include_runfiles = True,
    package_file_name = "openroad.tar",
)
```

The generated tarfile contains the binary "openroad" at root (as expected) plus the binary again at openroad.runfiles/_main/openroad. 

The tarfile should only contain the binary at the root level.