Strong dependencies (created by add_dependencies) must be honored when
linearizing a strongly-connected component of the target dependency
graph. The initial graph edges have strong/weak labels and can contain
cycles that do not consist exclusively of strong edges. The final graph
never contains cycles so all edges can be strong.
A recent change fixed a case in which CMake incorrectly diagnosed a
circular dependency involving a non-linkable executable target. This
adds a test for that case.
- Make sure the original link line is untouched
- Avoid duplicating the link line when supporting version < 1.4
- Make sure the cyclic dependencies and such are output correctly in
complicated cases.
- Avoid outputing dependencies that are already satisfied on the original
link line when possible.