Added message that warns the user that building all available packages will take a LONG time

build/recipes/build_pkgs/build_pkgs.py

@@ -60,6 +60,9 @@ class Recipe:
         :return: Paths to files, as strings, created by the recipe.
         """
         if self.options['name'] == "all":
+            logger.warning("WARNING: You've requested all packages to be built. This will take a long time.")
+            logger.warning("If only one or a few packages have changed, consider specifying them "
+                           "in a comma-separated list.")
             pkgs = self.pkg_list
         else:
             pkgs = self.options['name'].split(',')