Eyre broken in rust-analyzer with nightly

[Noratrieb]

When using nightly, rust-analyzer is completely unable to resolve anything regarading eyre when using a nightly toolchain. I suspect this is because of the build script used here, which is why I'm opening the issue here and not with rust-analyzer. This probably does something with the build script that breaks rust-analyzer. (I personally really dislike these feature detection build scripts, I would prefer it if eyre just raised its MSRV to require everything it needs and deleted the build script, but I can understand if you don't want to do that).

When using the stable toolchain, it works perfectly fine.

[ten3roberts]

Hey there, this looks related to #84 , which is to be fixed by #160.

Would you mind giving the branch a spin?