cmake: report CI information in the configure output

This makes it easy to go from CDash back to the CI infrastructure.

CMake/vtkCI.cmake

+if (NOT DEFINED ENV{CI})
+  return ()
+endif ()
+
+if (DEFINED ENV{GITLAB_CI})
+  message(STATUS
+    "GitLab CI Pipeline: $ENV{CI_PIPELINE_URL}")
+  message(STATUS
+    "GitLab CI Job: $ENV{CI_JOB_URL}")
+  if (DEFINED ENV{CI_MERGE_REQUEST_PROJECT_URL})
+    message(STATUS
+      "GitLab Merge Request: $ENV{CI_MERGE_REQUEST_PROJECT_URL}/-/merge_requests/$ENV{CI_MERGE_REQUEST_IID}")
+  endif ()
+  if (DEFINED ENV{CI_PIPELINE_SCHEDULE_DESCRIPTION})
+    message(STATUS
+      "GitLab Scheduled Pipeline: $ENV{CI_PIPELINE_SCHEDULE_DESCRIPTION}")
+  endif ()
+else ()
+  message(STATUS
+    "CI detected, but no known backend")
+endif ()

CMakeLists.txt

@@ -12,6 +12,7 @@ endif ()
 
 set(vtk_cmake_dir "${VTK_SOURCE_DIR}/CMake")
 list(INSERT CMAKE_MODULE_PATH 0 "${vtk_cmake_dir}")
+include(vtkCI)
 
 if (APPLE)
   include(vtkApple)