So, what you are saying is that you want to program a frequency counter running on CLK2 to time CLK1, a counter with really poor accuracy. If that counter sees 100MHz, then you turn off the reset, if it does not see 100MHz, then you turn on the reset.
Doesn't sound too difficult. You only need an accuracy of ~3 bits, where your counter total being 0= no clock, 1=25mhz, 2=50mhz, 3=75mhz, ect... if the result is 3 or larger, then the CLK1 is ~100mhz.
You can also make a counter which resets once every mhz, then you will know the frequency of clk1 within 1 mhz, but you would need a 7 bit counter to see the 99-101mhz result.