Replace reflection usage when preparing linker pipeline

[radekdoulik]

Context: #4669

We are temporarily using reflection to modify pipeline in SetupStep. This should be replaced by using cmd line arguments (--custom-step) and relevant msbuild parts or by using Pipeline API.

It is not clear yet whether the Pipeline API would be public. I would like to wait before redoing the temporary solution until later when it will be more clear whether we might need pipeline steps removal/replacement or not.

[jonathanpeppers]

I think this was fixed in: #5748