new tcmalloc crashes on ubuntu 20.04

the rgw suite just started hitting a tcmalloc crash on main against ubuntu 20.04: https://tracker.ceph.com/issues/59269 this happens during startup of one of our librgw_file test cases https://tracker.ceph.com/issues/58219 tracks a similar crash from the fs suite in december, which apparently went away after reverting a change to ceph-dencoder's linkage, but it doesn't sound like we ever found the root cause is this crash showing up anywhere else? has anything changed with respect to tcmalloc versions or linkage recently?