Patch results are only displayed once per invocation of CMake (#292)

Instead of showing the patch status for each call to `rapids_cpm_<pkg>` only display it on the first. This makes it clearer that we aren't applying the patches multiple times.

Authors:
  - Robert Maynard (https://github.com/robertmaynard)

Approvers:
  - Vyas Ramasubramani (https://github.com/vyasr)

URL: #292

rapids-cmake/cpm/detail/display_patch_status.cmake

@@ -29,12 +29,15 @@ Displays the result of any patches applied to the requested package
 
 #]=======================================================================]
 function(rapids_cpm_display_patch_status package_name)
-  list(APPEND CMAKE_MESSAGE_CONTEXT "rapids.cpm.display_patch_status")
-  set(log_file "${CMAKE_BINARY_DIR}/rapids-cmake/patches/${package_name}/log")
-  if(EXISTS "${log_file}")
-    file(STRINGS "${log_file}" contents)
-    foreach(line IN LISTS contents)
-      message(STATUS "${line}")
-    endforeach()
+  # Only display the status information on the first execution of the call
+  if(${package_name}_ADDED)
+    list(APPEND CMAKE_MESSAGE_CONTEXT "rapids.cpm.display_patch_status")
+    set(log_file "${CMAKE_BINARY_DIR}/rapids-cmake/patches/${package_name}/log")
+    if(EXISTS "${log_file}")
+      file(STRINGS "${log_file}" contents)
+      foreach(line IN LISTS contents)
+        message(STATUS "${line}")
+      endforeach()
+    endif()
   endif()
 endfunction()