Allow for sharing SDK's cmake setup between multiple projects in a single (CMAKE) root

[stefanct]

I tried to build multiple binaries (for RT1020 and RT1024) on the command line using the SDK's cmake in a shared build directory. To that end, I include core/cmake/mcux.cmake once per project after configuration (e.g., calling add_executable()) in the respective CMakeLists.txt files of the projects. Unlike the SDK examples I would like to be able to process the whole directory tree of projects with cmake in a single run.

There are some minor(?) changes required in the SDK to do this successfully:

1. The custom targets in cmake/kconfig.cmake require to have unique names across projects (instead of all projects having a single menuconfig etc). I have simply prefixed them with ${PROJECT_NAME}_ (e.g., instead of make menuconfig one has to call make hello_menuconfig).
2. In the CMSIS submodule's set_CMSIS.cmake the include guard needs to be changed to DIRECTORY scope. The current global scope prohibits configuration of cmsis for all but the very first project. I did not notice any ill effects from this. Is there a rationale for the global guard?

Neither of these changes breaks the functionality when using cmake in single projects as before AFAICT. However, of course the command names change, which might surprise users and requires some documentation changes, if implemented.
In large deployments like the SDK's example repository the approach with single, separated projects is probably way more desirable but it's a restriction that is not necessary and complicates some setups, e.g., where libraries are built and used in the same cmake tree.

[mcuxsusan]

Hi @stefanct, thanks for all recent feedback to our experimental version of kconfig+cmake design, this is very valuable to us! The development team is working on re-design of kconfig+cmake for our SDK, they will take your suggestions and try to meet the requirement in the design.