[llvm] MCFragment: Use trailing data for fixed-size part (PR #150846)

[Nikolay Panchenko via llvm-commits]

npanchen wrote:

@MaskRay our pulldown also identified same problem as @chelcassanova reported above.
That reminded me of https://github.com/llvm/llvm-project/pull/148544#issuecomment-3079636231 issue of ~2w ago right in the same place and it seems make more sense to add an assert there.
Are you working on a fix or this commit can be reverted for now ?

https://github.com/llvm/llvm-project/pull/150846