Summary:
I noticed mvfst and proxygen started breaking on my other getdeps changes, turns out it wasn't my diffs, it was that the the packaged cmake was now too old for them.

Fix it by packaging 3.20.2 which matches the system version on centos stream 8, which I found works

Reviewed By: bigfootjon

Differential Revision: D32805140

fbshipit-source-id: adfeb625c1df112bb28a743531cf34473cb734c3