Configure used cmake compiler

[baszalmstra]

Currently the cmake build backend always selects the `cpp` compiler. When we want to use CUDA we also need to add ${{ compiler("cuda") }}.

We want to keep using a sane default ("cpp", or magic in the future) but if the user explicitly configure it, it should also be possible to overwrite this behavior:

[package.build.configuration]
compilers = ["cpp"] # If not specified this will be the default
compilers = ["cpp", "cuda"]