Update readme to reflect #28260 and a workaround

[SingingTree]

This PR adds a note to the end of the Windows build instructions to reflect the issues detailed in #28260, as well as a work around using older versions of gcc. I've avoided going into detail as I did not wish to bloat the README, and so that the changes are easy to yank once the issue is resolved.

[rust-highfive]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @brson (or someone else) soon.

If any changes to this PR are deemed necessary, please add them as extra commits. This ensures that the reviewer can see what has changed since they last reviewed the code. The way Github handles out-of-date commits, this should also make it reasonably obvious what issues have or haven't been addressed. Large or tricky changes may require several passes of review and changes.

Please see the contribution instructions for more information.

[alexcrichton]

Could you link to the relevant issue from here as well? That way once it's closed this'll be at least a "little updated"!

[SingingTree]

Sure thing. To clarify: link to #28260 in the README?

[alexcrichton]

Yeah just a mention that there's a tracking issue for this weird behavior

[SingingTree]

Sorted.

[alexcrichton]

@bors: r+ a17d77b

[bors]

⌛ Testing commit a17d77b with merge 0be1bcd...

[bors]

☀️ Test successful - auto-linux-32-nopt-t, auto-linux-32-opt, auto-linux-64-debug-opt, auto-linux-64-nopt-t, auto-linux-64-opt, auto-linux-64-x-android-t, auto-linux-cross-opt, auto-linux-musl-64-opt, auto-mac-32-opt, auto-mac-64-nopt-t, auto-mac-64-opt, auto-win-gnu-32-nopt-t, auto-win-gnu-32-opt, auto-win-gnu-64-nopt-t, auto-win-gnu-64-opt, auto-win-msvc-32-opt, auto-win-msvc-64-opt