pro2cmake: Do not error out if $$files is called with a 2nd parameter

Do not stop the whole conversion if we encounter $$files(..., true).
Ignore the 2nd parameter for now.

Change-Id: If9334ce9719b98c33716dc7f18ba8aede05fe8b1
Reviewed-by: Leander Beernaert <leander.beernaert@qt.io>
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>
Reviewed-by: Qt CMake Build Bot

util/cmake/pro2cmake.py

@@ -623,10 +623,6 @@ def handle_function_value(group: pp.ParseResults):
         return str(group)
 
     if function_name == "files":
-        if len(function_args) > 1:
-            raise RuntimeError(
-                "Don't know what to with more than one function argument for $$files()."
-            )
         return str(function_args[0])
 
     if isinstance(function_args, pp.ParseResults):