bug#70889: 29.3; GCC14.1 MinGW compilation error

[Cyril Arnould]

> So I'd like first to understand why a warning causes a compilation
> error.

This is a new feature of GCC 14, unless I'm misunderstanding
something:

https://gcc.gnu.org/gcc-14/porting_to.html#warnings-as-errors

> If we need to add to our w32 headers every single function that can
> fail the compilation of some test program, we will never recover
> from this slippery slope.

Would using the gnulib work instead of using emacs-proprietary w32
headers? Mostly asking out of curiosity.