[compiler-rt] [compiler-rt] Work around incompatible Windows definitions of (S)SIZE_T (PR #106311)

[Martin Storsjö via llvm-commits]

https://github.com/mstorsjo approved this pull request.

LGTM, this seems to work fine now. (I don't have a strong opinion on whether this is a good way of solving it or not though.)

https://github.com/llvm/llvm-project/pull/106311