check for guild run using RUN_DIR

Author: t-kalinowski

R/callbacks.R

@@ -799,8 +799,8 @@ normalize_callbacks <- function(callbacks) {
   })
 
   # add the tensorboard callback if necessary
-  if ((getOption("guildai.is_run_active", FALSE) ||
-       tfruns::is_run_active()) && !have_tensorboard_callback)
+  if ((nzchar(Sys.getenv("RUN_DIR")) || tfruns::is_run_active()) &&
+      !have_tensorboard_callback)
     callbacks <- append(callbacks, callback_tensorboard())
 
   # return the callbacks