bug#37801: Possible insight into issue #30756 #include_next bug

[Carl Dong]

Hi Danny,

Thank you so much for the links and quotes, I'm definitely going to refer back
to them in the future and you probably saved me dozens of hours :-)

> I think so. I can't figure out why Guix is not just setting up CROSS_CPATH
> on its own in the first place.
> gnu/packages/cross-base.scm DOES have a search-path specification for
> CROSS_CPATH.

Perhaps Ludovic can confirm this, but I believe the reason why Guix is not
setting up CROSS_CPATH is because it doesn't _know_ it's cross-compiling. Guix
only sets up CROSS_CPATH when we invoke on the command line with
--target=x86_64-w64-mingw32 or something like that. I'm not exactly sure what a
clean solution to this is, but I'd hope we can find one in the future.

I'm thinking that the reason why my final solution involved explicitly setting
the exact ordering in my CROSS_CPLUS_INCLUDE_PATH was because mingw-w64 is
considered to be libc and that makes it special somehow. Not 100% sure though.

Cheers,
Carl Dong
address@hidden
"I fight for the users"