[llvm] [RuntimeDyld][Windows] Allocate space for dllimport things. (PR #106958)

[Alastair Houghton via llvm-commits]

al45tair wrote:

The only difference between this and #102586 is two `override` specifiers; @bnbarham reviewed the previous incarnation. Assuming this passes all the checks, I plan on merging without additional review since the change from the previous version is very small.

https://github.com/llvm/llvm-project/pull/106958