Correctly export dependencies for downstream packages (backport #70)

[mergify]

This PR addresses #69.

Commit bb3c126 should be backported/cherry-picked for humble and jazzy branches.

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This is an automatic backport of pull request #70 done by Mergify.

[mergify]

Cherry-pick of e33a5e9 has failed:

On branch mergify/bp/jazzy/pr-70
Your branch is up to date with 'origin/jazzy'.

You are currently cherry-picking commit e33a5e9.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   draco_point_cloud_transport/CMakeLists.txt

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   plugin_template/CMakeLists.txt
	both modified:   zlib_point_cloud_transport/CMakeLists.txt
	both modified:   zstd_point_cloud_transport/CMakeLists.txt

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally