include filepath as __file__ in global scope

Signed-off-by: George Ridal <george.ridal@gmail.com>

src/rez/serialise.py

@@ -329,6 +329,7 @@ def _process(value):
 
                 # apply globals
                 fn.__globals__["this"] = EarlyThis(data)
+                fn.__globals__["__file__"] = filepath
                 fn.__globals__.update(get_objects())
 
                 # execute the function