add comment about why this shouldn't be used for everything

Framework/python/ldmxcfg.py

@@ -60,7 +60,12 @@ def from_file(cls, source_file, class_name = None, needs = [], instance_name = N
 
         Note
         ----
-        
+        Developing processors in this way is incredible inefficient, especially since it
+        does not allow for code to be well organized and split across many files nor does it
+        allow for two processors to share common code.
+        If you find yourself defining more than one `class` within your new C++ processor,
+        it is highly recommended to transition your workflow to including your processor as a
+        part of ldmx-sw so that it can fully benefit from a build system.
 
         Parameters
         ----------