If you take a look at the datasheet for the ATtiny13, you'll see that the reset pin can be used as a "weak" I/O line, meaning it can't perform the same as other I/O lines. On page 140, there are graphs showing the current sinking characteristics vs the output voltage; notice how much less the values are than the other I/O lines shown in the prior pages. Are you operating within the specifications?
Other things to check:
- Have you tried to talk to the chip since to verify that the RESET line is disabled?
- Do you have verification that your code was actually programmed to the chip? (AVRDUDE output)
- Are you sure your series resistor value is correct?
- Are you sure you have your LED in the correct orientation?
As noted in the comments, using the reset line for I/O means the only ways to reprogram your chip are with a bootloader or "High-Voltage Serial Programming" so it isn't something you should do unless you are out of I/O lines and have an alternative means of programming the chip.
Also of note, you have defined F_CPU to be 8MHz, but your low fuse Value of 0x6A implies that the "Clock divide" fuse is enabled, so your CPU frequency is actually 1MHz.
A few final notes:
- It's always a good idea to "decouple" the VCC line with a 0.1uF ceramic capacitor to GND
- You don't need a "return" statement from main in embedded systems. Where would it return to?
- I'd suggest using the pin macros such as _BV(PB5) or (1 << PB5) rather than the explicit 0b0010000 - it compiles to the same thing
rather than set, delay, clear, delay, just toggle the pin as such:
PORTB ^= _BV(PB5);