Looks good to me, but it wouldn't harm to add a CI test for clang with gnu frontend targetting msvc abi.
How does CMake need to be configured compared to when using clang-cl?

You just use clang as compiler instead of clang-cl and use GNU style flags. I'll take a look at adding a test

This is only required in 1.81+, so temporarily bumping rust version in CI to make sure it fails with the expected error, then i'll un-revert

I'm realizing if we had just updated corrosion it would have worked fine because of #537, oops.

I still think this is a good change, but I'll fix it's interaction with 537

I'm realizing if we had just updated corrosion it would have worked fine because of #537, oops.

I'm confused now - Is the -Wl, not needed after all? There are also other libraries that rustc requires us to link for msvc, so I would have expected to see a CI failure if Wl, was required (on the "bump again?" commit).

The -Wl, is required when using clang to invoke the linker.

This fix isn't necessary in my case because #537 removes /defaultlib:msvcrt entirely from the link flags, and it was the only link flag being passed, so there are no flags that need prefixing with -Wl,.

So this change is still correct, just not needed on the current rust compiler which /defaultlib:msvcrt is the only flag it reports.