[llvm] [InstrRef][nfc] Remove usage of unique_ptrs of arrays (PR #74203)

[Felipe de Azevedo Piovezan via llvm-commits]

felipepiovezan wrote:

> Note that this is only for the final linker invocation, so you'd want to run ninja -v to get the final clang invocation that performs LTO and run that under time

This is what I tried when repro-ing that experiment.
I will try to use a vm and run it under valgrind

https://github.com/llvm/llvm-project/pull/74203