Added some more help on how to hook up MCU pins
interrupt driven debounce not working
latest
Wrong clock connection for programmer

Serial clock on the ISP6 connector was connected to pin 2 on our ATtiny13. It should have been pin 7.
Pin 2 is for external generation of clock signal. E.g. where you put a crystal. It has nothing to do with
the clock for serial communication which is on pin 7. pin7 is what you use for In System Programming.

Getting this wrong created a very hard to debug error message from avrdude. The same error message you got
for not having any connections to the AVR chip.