We have a bunch of repo specific qtbase.yaml, qtsvg.yaml, etc files in qt5.git/coin/platform_configs to enable CMake build of various repos.

We need to extract all the duplicate information into a common file which will be included in all those .yaml files. We need COIN-538 in production for that.

It's a bit of manual work, but still reduces a lot of duplication.

We can't add the cmake configurations to default.yaml because it's used by all repositories, and thus any repository that has no cmake port will fail to build.