feat: add CMakeLists.txt to support CPM

[aminya]

Co-Authored-By: @ClausKlein

Cherry-picked from #105

• test that Conan works in the projects that use project_options

[ClausKlein]

Great.
By the way, xhy do you not use a symbolic link to Index.cmake?

[aminya]

Great.
By the way, xhy do you not use a symbolic link to Index.cmake?

Because symlinks on Windows require admin permission

[aminya]

@ddalcino Could you test this change with Conan? I don't have many Conan projects to test this with

[ddalcino]

@ddalcino Could you test this change with Conan? I don't have many Conan projects to test this with

I must be missing some context here. I'm not sure what you're asking for. I can test this manually with CMake Package Manager if that will help. As I understand it, CPM is the package manager that needs this change?

Are you asking me to create a Conan package that uses project_options, and see if I can use it in a dependent project? That's probably a good idea, but I think it should be tested continuously rather than as a one-off.

[ClausKlein]

@ddalcino Could you test this change with Conan? I don't have many Conan projects to test this with

I tested under ubuntu this: https://github.com/ClausKlein/cpp_starter_project/commit/d690b81ec76351218bf8b08d52651fd2ceb3f474

and here
cpp-best-practices/gui_starter_template#207

[ddalcino]

I have tested this, and I can confirm that it works as intended. CI logs are here: https://github.com/ddalcino/cpp_starter_project/actions/runs/2072971834

For completeness, I have also verified that CPM does not load project_options properly without this change.

I think it could be really useful to add directions to the README about how to fetch project_options properly using CPM; I didn't know how to do it myself.

[aminya]

Thanks for the testing!