If you are down to cutting the bolt away from the bush, an air saw is great, you can do it with a hand pad saw, takes a lot longer though
You can get the saw through the gap between the bracket and arm
If you have enough room a reciprocating electric saw may do the job, but use good quality hacksaw blades whichever tool you use, it makes all the difference, a bit of lubricant will stop over heating (wd40 etc)
I used the air saw on a self leveller piston on the back axle of the hybrid (rangy) that was about1 1/2 inches thick, took about 45 mins
You may be able to get an angle grinder with a metal cutting disk down the gap but you may take some of the betal off the arm or bracket that way