[llvm] [MC] Allocate MCFragment with a bump allocator (PR #96402)

[Nikita Popov via llvm-commits]

nikic wrote:

It looks like this change has massively increased memory usage, see https://llvm-compile-time-tracker.com/compare.php?from=fc23564c44f3eff1847462253d43c08b85489148&to=8cb6e587fd40b97983e445ee3f17f4c6d7190df7&stat=max-rss&linkStats=on. ReleaseLTO-g linking max-rss goes up by up to 7%.

https://github.com/llvm/llvm-project/pull/96402