[llvm] [llvm-dwp] Replace MCStreamer with direct ELF writer for zero-copy output (PR #192112)

[Farid Zakaria via llvm-commits]

fzakaria wrote:

@MaskRay hmmm.
I see https://github.com/MaskRay/llvm-project/commit/8d731c0cb62f1aaab9f8fa44aa1c1c5bfd68e754#diff-838884125b7fdaba29e05a33f3e57df8aca374c481dc181a9e4e014817774627R1148 which is a large memory allocation I think.

Won't that be large for the benchmarks of large files?
I think the biggest benefit of the refactor I hoped to pursue is the immediate streaming out via StringRef to avoid any copies.

I can look into the bug the AI review brought up "Exposed a latent bug in the PR." if the current approach is how we'd like to proceed.

I'm hesitant for a refactor that consolidates code but doesn't actually retain any performance improvements that were the initial goal -- at least in the spirit of what I was trying to achieve. :upside_down_face:  :bow: 

https://github.com/llvm/llvm-project/pull/192112