[llvm] RuntimeLibcalls: Fix building hash table with duplicate entries (PR #153801)

[Eli Friedman via llvm-commits]

https://github.com/efriedma-quic approved this pull request.

Using a power-of-two hashtable size means you're really relying on a strong hash function; allowing non-power-of-two functions gives a lot more chances to cover up any imperfection.  We might want to consider adding a diagnostic if MaxCollisions gets excessively high.

Otherwise LGTM

https://github.com/llvm/llvm-project/pull/153801