How long does it takes for arduino to reach main()?
The ATtiny85 has a built-in delay counter that keeps the MCU in reset
mode for some time after the power is applied. This seems to be intended
as a wait for the clock and power to be stabilized. The length of this
delay depends on your selected clock source, and is somewhat
configurable with the fuses.

According to your code, your MCU is clocked at 8&nbsp;MHz. I assume you
are then using the internal RC oscillator as a clock source. If this is
the case, you have three choices for the startup delay:


20 CPU cycles
20 CPU cycles + 4 ms
20 CPU cycles + 64 ms


The latter is recommended if your power rises slowly, and is the default
configuration in which these MCUs are shipped. If you power level rises
fast, you may want to select a shorter delay by programming the SUT
fuses. See the datasheet for details (section System Clock and Clock
Options → Clock Sources → Calibrated Internal Oscillator).