Manifest example test doesn't work

## Expected Behavior

All examples work.

## Actual Behavior

```
$ bazel test //examples/manifest:main_test
ERROR: /workspaces/rules_license/examples/manifest/BUILD:25:15: in cmd attribute of genrule rule //examples/manifest:gen_main_manifest: label '//examples/manifest:main_manifest' in $(locations) expression expands to no files. Since this rule was created by the macro 'android_binary', the error might have been caused by the macro implementation
ERROR: /workspaces/rules_license/examples/manifest/BUILD:25:15: Analysis of target '//examples/manifest:gen_main_manifest' failed
ERROR: Analysis of target '//examples/manifest:main_test' failed; build aborted:
INFO: Elapsed time: 0.154s
INFO: 0 processes.
FAILED: Build did NOT complete successfully (1 packages loaded, 6 targets configured)
ERROR: Couldn't start the build. Unable to run tests
```

## Steps to Reproduce the Problem

1. `bazel test //examples/manifest:main_test`

## Specifications

- Version:
- Platform:

Start by inspecting examples/manifest/BUILD around line 25 and the gen_main_manifest target referenced in the Bazel error. Run bazel test //examples/manifest:main_test while investigating why the main_manifest label expands to no files. Done means the command completes successfully and all manifest examples work.

Written by the indexing model from the issue text.