Investigate further the "merged_output" functions

[sleemanj]

Merged #6

I think we might be able to either get rid of these scripts entirely by adjusting that recipe in platform.txt, or at least add support for them to boards.txt.

ATTinyCore seems to hard-code the first parameter to the script (as in, it's not selectable by menu) so it may be that it was due to there being a problem with how Arduino creates merged output and not working on some chips?

I think that just dropping the scripts in place probably makes them do nothing because we are not providing that option, so this may not be exactly the intended operation - that is, do the merged outputs work at all.