Add pixi support in the robotology-superbuild

[traversaro]

As I frequently need to debug problems in the superbuild, the process of manually creating the conda environment to build a fresh superbuild was quite a slow down. Furthermore, whenever there is a dependency regression, the need to manually inspect the CI log is not really user friendly.

In this PR, we add the pixi.toml support to the superbuild, so you can just download the superbuild and run pixi run build-all to build the superbuild with all the options enabled. This is personally quite useful for me to work on the superbuild, but I guess it may be useful for other superbuild users. It has also the nice byproduct of ensuring that each release has a working lockfile of dependencies that work fine for a given release, quite useful if someone needs to get older releases of the superbuild to work.

At the moment, I am not modifying the existing conda instructions to avoid confusing existing users, but with time we could modify them as well (for example, we could generate conda lock files with https://github.com/synapticarbors/pixi2ces or similar, and use the lockfiles also when users are installing dependencies via conda.

[traversaro]

Agh, the CI is failing with:

CMake Error at .build/_deps/ycm-src/modules/YCMEPHelper.cmake:326 (message):
  Failed to get git name.  Please set it with "git config --global user.name
  Firstname Lastname" or from your favorite git gui.
Call Stack (most recent call first):
  .build/_deps/ycm-src/modules/YCMEPHelper.cmake:1021 (_ycm_setup_git)
  cmake/BuildYCM.cmake:8 (ycm_ep_helper)
  .build/_deps/ycm-src/modules/FindOrBuildPackage.cmake:205 (include)
  cmake/BuildYARP.cmake:8 (find_or_build_package)
  .build/_deps/ycm-src/modules/FindOrBuildPackage.cmake:205 (include)
  cmake/RobotologySuperbuildLogic.cmake:68 (find_or_build_package)
  CMakeLists.txt:68 (include)

I can't remember how many times in my life I saw this and had to deal with it, either adding the NON_INTERACTIVE_BUILD option or setting those values, even if the value was actually never used. For now I just added a workaround in the CI, but I think we should finally fix this.

[traversaro]

Agh, the CI is failing with:

CMake Error at .build/_deps/ycm-src/modules/YCMEPHelper.cmake:326 (message):
  Failed to get git name.  Please set it with "git config --global user.name
  Firstname Lastname" or from your favorite git gui.
Call Stack (most recent call first):
  .build/_deps/ycm-src/modules/YCMEPHelper.cmake:1021 (_ycm_setup_git)
  cmake/BuildYCM.cmake:8 (ycm_ep_helper)
  .build/_deps/ycm-src/modules/FindOrBuildPackage.cmake:205 (include)
  cmake/BuildYARP.cmake:8 (find_or_build_package)
  .build/_deps/ycm-src/modules/FindOrBuildPackage.cmake:205 (include)
  cmake/RobotologySuperbuildLogic.cmake:68 (find_or_build_package)
  CMakeLists.txt:68 (include)

I can't remember how many times in my life I saw this and had to deal with it, either adding the NON_INTERACTIVE_BUILD option or setting those values, even if the value was actually never used. For now I just added a workaround in the CI, but I think we should finally fix this.

Related issue: robotology/ycm-cmake-modules#455 .

[traversaro]

macos-14 builds fail with:

 CMake Error at /Users/runner/work/robotology-superbuild/robotology-superbuild/.pixi/envs/default/lib/cmake/Qt6/QtPublicDependencyHelpers.cmake:258 (message):
  To use a cross-compiled Qt, please set the QT_HOST_PATH cache variable to
  the location of your host Qt installation.
Call Stack (most recent call first):
  /Users/runner/work/robotology-superbuild/robotology-superbuild/.pixi/envs/default/lib/cmake/Qt6/Qt6Dependencies.cmake:10 (_qt_internal_setup_qt_host_path)
  /Users/runner/work/robotology-superbuild/robotology-superbuild/.pixi/envs/default/lib/cmake/Qt6/Qt6Config.cmake:124 (include)
  /Users/runner/work/robotology-superbuild/robotology-superbuild/.pixi/envs/default/lib/cmake/vtk-9.3/VTK-vtk-module-find-packages.cmake:1196 (find_package)
  /Users/runner/work/robotology-superbuild/robotology-superbuild/.pixi/envs/default/lib/cmake/vtk-9.3/vtk-config.cmake:159 (include)
  /Users/runner/work/robotology-superbuild/robotology-superbuild/.pixi/envs/default/share/pcl-1.14/PCLConfig.cmake:267 (find_package)
  /Users/runner/work/robotology-superbuild/robotology-superbuild/.pixi/envs/default/share/pcl-1.14/PCLConfig.cmake:316 (find_VTK)
  /Users/runner/work/robotology-superbuild/robotology-superbuild/.pixi/envs/default/share/pcl-1.14/PCLConfig.cmake:556 (find_external_library)
  cmake/YarpFindDependencies.cmake:378 (find_package)
  CMakeLists.txt:60 (include)

this is basically due to conda-forge/qt-main-feedstock#273 . I can manually add a local workaround for now.

[traversaro]

Merging as soon as CI passes as it is middle of August in a weekend, so hardly anyone could look into that. Furthermore, this just adds a workflow, it does not modify an existing one.