There are a large number of long standing issues with coroutines on
x86_32 windows as discussed here
https://github.com/llvm/llvm-project/issues/59382
- #59382
- #58556
- #58543
- #56989
- #193161
- #136481
As such this patches
- No longer defines `__cpp_impl_coroutine` on that platform
- Warn when using coroutines on that platform
The reason to not plainly error is that it would break too much valid
valid code, ie there are people who probably use coroutines sucessfully.
And we also want to keep testing on that platform, up until the point we
were to pull support completely.
Hopefully this is all temporary and someone will feel compelled to
improve the situation enough that we can unceremoniously revert this
patch.
94e0fd0988