Custom Solenoid design and control
The simple answer is indeed simple - you can't do it. If you really want to continue on this path you'll have to do one of two things.

1) Use the relay to energize the coil of a much beefier relay, called a contactor, which is rated for at least 100 amps. A note of caution: they're expensive.

2) Take your solenoid, and rewind it so as to use 10 times as much wire, which will give you (more or less) 10 times as many turns. With 10 times the wire length the current at 12 volts will be 1/10 what you're drawing now, but the magnet will be just as strong. Now you can use your 10 amp relays to energize the coil.

Whichever you do, you'll need to be careful about running your coil for any length of time. The power dissipated in the solenoid is volts times current, and in your case that's 90 amps times 12 volts, or 1080 watts. The internal windings of the solenoid will get very hot, very quickly. Since I assume you're using fairly cheap wire, you'll melt the insulation in minutes (or maybe less).