[llvm-branch-commits] [NFCI][ELF] Introduce explicit Computed state for DynamicReloc (PR #150799)

[Jessica Clarke via llvm-branch-commits]

https://github.com/jrtc27 created https://github.com/llvm/llvm-project/pull/150799

Currently we set the kind to AddendOnly in computeRaw() in order to
catch cases where we're not treating the DynamicReloc as computed.
Specifically, computeAddend() will then assert that sym is nullptr, so
can catch any subsequent calls for relocations that have sym set.
However, if the DynamicReloc was already AddendOnly (or
MipsMultiGotPage), we will silently allow this, which does work
correctly, but is not the intended use. We also cannot catch cases where
needsDynSymIndex() is called after this point, which would give a
misleading value if the kind were previously against a symbol.

By introducing a new (internal) Computed kind we can be explicit and add
more rigorous assertions, rather than abusing AddendOnly.