Add flag to also add build-dep for runtime-depends

[harrysarson]

Superflore is correct to generate runtime dependencies when an
dependency is needed to provide headers and libraries needed to consume
an element but not to build it. Some tooling struggles to interpret the
c/c++ dependency graph when the dependencies are represented as
runtime-dependencies.

This commit adds a flag to additionally generate a build-dependency
for elements that depend on a ROS package that defines a package as
a runtime dependency.

[tom--pollard]

additional generate -> additionally generate in the commit message

[tom--pollard]

It might just be me, but commit body doesn't match up to the commit title to me? The title references the addition of a build-dep, but the body describes the ability to control a runtime dep? Could just be me being confused though

[harrysarson]

The title references the addition of a build-dep, but the body describes the ability to control a runtime dep?

For test build[tool]-export-dependencies we already generate a runtime-dep and with this commit also generate a build-dep. Let me try and update to make this clearer.

[harrysarson]

Ah! Looking at the code the comment is out of date, we do this for all runtime dependencies. I should update the commit message and also the flag name