[llvm] Implement reserveAllocationSpace for SectionMemoryManager (PR #71968)

[Graham Markall via llvm-commits]

gmarkall wrote:

Now that [numba/llvmlite#1009](https://github.com/numba/llvmlite/pull/1009) (which essentially implements the same changes made here, just inside llvmlite) is merged and an RC has been produced, I've received various reports that this fixes issues related to #71963 on both macOS and LinuxAArch64 systems, and no reports of adverse effects - so FWIW, my confidence in this patch being a good fix is quite high.

https://github.com/llvm/llvm-project/pull/71968