##### SUMMARY
If you have executable files in your source code they are not kept in the tarball.

Could be related to https://github.com/ansible/ansible/blob/99d7f150873011e7515851db9b44ff486efa9d77/lib/ansible/galaxy/collection.py#L763

This was noticed as I had some auxiliary scripts in my repo.

Need to also consider scripts in `files/` if/when Collections support roles.

This seems to fail the "principal of least suprise"

**Proposal 1: Keep on stripping executable flags**

Add some line to the output
`WARNING: tests/coverage.sh: source file has executable flag, though this will be ignored in generated tar.gz`
Update developing a collection documentation page
Update integration tests to ensure that executable mode is always stripped.
Update code to link to this issue

**Proposal 2: Allow executible flags**

Update developing a collection documentation page
Update integration tests to ensure that executable mode is preserved
Update code to link to this issue
Changelog


##### ISSUE TYPE
- Bug Report

##### COMPONENT NAME
ansible-galaxy

##### ANSIBLE VERSION
```paste below
2.10
```

##### STEPS TO REPRODUCE
<!--- Describe exactly how to reproduce the problem, using a minimal test-case -->

<!--- Paste example playbooks or commands between quotes below -->
```yaml

```

<!--- HINT: You can paste gist.github.com links for larger files -->


if missing_keys:
        raise AnsibleError("The collection galaxy.yml at '%s' is missing the following mandatory keys: %s"
                           % (to_native(b_galaxy_yml_path), ", ".join(sorted(missing_keys))))
    extra_keys = set_keys.difference(all_keys)
    if len(extra_keys) > 0:
        display.warning("Found unknown keys in collection galaxy.yml at '%s': %s"
                        % (to_text(b_galaxy_yml_path), ", ".join(extra_keys)))
    
    for optional_string in string_keys:
        if optional_string not in galaxy_yml:
            galaxy_yml[optional_string] = None
    for optional_list in list_keys:
        list_val = galaxy_yml.get(optional_list, None)
        if list_val is None:
            galaxy_yml[optional_list] = []
        elif not isinstance(list_val, list):
            galaxy_yml[optional_list] = [list_val]
    for optional_dict in dict_keys:
        if optional_dict not in galaxy_yml:
            galaxy_yml[optional_dict] = {}
    
    galaxy_yml['license_ids'] = galaxy_yml['license']
    del galaxy_yml['license']
    return galaxy_yml
def _build_files_manifest(b_collection_path, namespace, name, ignore_patterns):
    
    
    b_ignore_patterns = [
        b'galaxy.yml',
        b'*.pyc',