Not that I think it would work, but let's face it... there was only six gholam ever made. Do you really think anyone lost time trying to throw stuff at them in the wild possibility some matters might harm it, or that many who got as close to them as Mat ever survived the encounter?

It's a complete strike of luck from the luckiest man alive that in the fight the medallion came in contact with the gholam and Mat discovered the medallion could harm it.

Most likely, the way gholam were killed (assuming any were killed and the 5 others didn't simply died in the breaking and only one was put in stasis and survived) or would be killed in the WOS would quite simply be with deathgates. That's the first thing an AS back then would think about to kill an unknown construct. It wouldn't be easy because they're fast, and very rare, so I'm guessing most AS who encountered one of the six gholam died at its hands, because by the time they realised what it was, and that it was immune to the OP, it was already too late to do anything.

The medallion aside, a believable way the gholam might be killed is if Elayne puzzle out how the medallion was made, and the principles behind it. If she has access to the materials, she could make a weapon that could kill a gholam. But given that it would all be theorical and she'd gamble her life trying to prove it works, I'd say that's unlikely. In a war with gholam involved and scientists in labs this would be realistic, but with Elayne this would look terribly "arranged" and convenient.