[clang] [compiler-rt] [asan][windows] Eliminate the static asan runtime on windows (PR #81677)

[Reid Kleckner via cfe-commits]

https://github.com/rnk commented:

Is it feasible to create a migration path from the static runtime to the dynamic runtime? As written, this requires users to update their ASan builds at the same time that they take this update. Is it possible to leave the static runtime behind, create a migration path to the dynamic runtime (add all the new weak symbol registration functionality), push that, and then follow up by removing the static runtime 2-4 weeks later?

The sanitizer runtimes are not ABI-stable, so I think we're free to remove the static runtimes without leaving behind some kind of compatibility layer. This isn't libc++.

I also don't want to overindex on Google's or Chromium's needs. Many folks use the open source releases produced every six months, so to really accommodate those users, we'd have to delay the removal across a release boundary. I'm advocating for that, but it's worth considering depending on the cost.

I believe the first four patches can land separately if we agree on the direction.

https://github.com/llvm/llvm-project/pull/81677