Coverage builds of examples are not tested in CI

[scpeters]

Environment

• OS Version:
• Source or binary build?

Description

• Expected behavior: our examples should be built with the Coverage build type in CI
• Actual behavior: that build type is not tested because lcov is not installed during that phase of the build (first noticed in https://github.com/gazebosim/gz-cmake/pull/437#issuecomment-2241295897)

Steps to reproduce

1. Run a CI job
2. Search console log for Install configuration: "Coverage"
3. It would be found if our CI was testing coverage builds of examples, but it is not

Output