[llvm] [llvm][Support] Add indirection to call correct validate(...) function (PR #71966)

[via llvm-commits]

arrv-sc wrote:

> Is this a similar problem to what `detail::doMapping` is solving for the mapping function? Perhaps we could structure this the same way for consistency?

I actually agree with you. Updated.

https://github.com/llvm/llvm-project/pull/71966