ci: Move cppyy job to build stage to speed up pipeline
Move the cppyy
job to the build
stage to speed up the pipeline.
Currently, all jobs in the test
stage start immediately after the corresponding jobs in the build
stage finish. However, the cppyy job only starts after all jobs in the build
stage finish. By that time, the jobs in the test
stage are already well ahead and the whole pipeline will be stuck until the cppyy job also finishes.