Download spdlog with all the right settings

rapids-cmake/cpm/rapids_logger.cmake

@@ -43,6 +43,29 @@ Result Functions
 function(rapids_cpm_rapids_logger)
   list(APPEND CMAKE_MESSAGE_CONTEXT "rapids.cpm.rapids_logger")
 
+  # TODO: Need to also support this in exported config files so that header-only libraries like rmm
+  # can force their consumers to clone spdlog when a pre-built package is found.
+  if(RAPIDS_LOGGER_HIDE_ALL_SPDLOG_SYMBOLS)
+    get_property(_already_downloaded_spdlog GLOBAL PROPERTY RAPIDS_LOGGER_DOWNLOADED_SPDLOG)
+    if(NOT _already_downloaded_spdlog)
+      if(TARGET spdlog::spdlog)
+        message(FATAL_ERROR "Expected spdlog::spdlog not to exist before the first call to rapids_cpm_rapids_logger when RAPIDS_LOGGER_HIDE_ALL_SPDLOG_SYMBOLS is ON"
+        )
+      endif()
+      set(CPM_DOWNLOAD_spdlog ON)
+      rapids_cpm_spdlog(FMT_OPTION "BUNDLED"
+                        # TODO: Get the export sets as input
+                        INSTALL_EXPORT_SET ${_RAPIDS_EXPORT_SET}
+                        BUILD_EXPORT_SET ${_RAPIDS_EXPORT_SET}
+                                         # TODO: I don't really expect this to work with the way
+                                         # that rapids_cpm_spdlog is set up right now, it's going to
+                                         # require some tweaking of argument forwarding I suspect.
+                                         CPM_ARGS EXCLUDE_FROM_ALL ON OPTIONS
+                                         "BUILD_SHARED_LIBS OFF" "SPDLOG_BUILD_SHARED OFF")
+      set_property(GLOBAL PROPERTY RAPIDS_LOGGER_DOWNLOADED_SPDLOG ON)
+    endif()
+  endif()
+
   set(options)
   set(one_value)
   set(multi_value)