fix for fscanf wrappers in static linking
When using Darshan's static libraries, we were still passing the
--wrap argument for
__isoc99_fscanf regardless of whether we detected we should include that wrapper at config time (based on !35 (merged)). This fix updates the STDIO module ld options to only include the
__isoc99_fscanf if the config test does not pass (i.e., fscanf is not implemented using redirection).