[llvm] [Support] Report OOM from `allocate_buffer` (PR #85449)

[Nikita Popov via llvm-commits]

nikic wrote:

No significant impact: https://llvm-compile-time-tracker.com/compare.php?from=3057d0f14af5e073be3b7c7942dfff2a975ac4cb&to=8fec8653411d09bca427c8bae49593fe99d92e27&stat=instructions:u

https://github.com/llvm/llvm-project/pull/85449