bug#75194: Compilation of latest `scratch/igc' fails with `xwidget' on MacOS

[Pip Cet via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

Pip Cet <pipcet@protonmail.com> writes:

> 黄京 <radionoisee@gmail.com> writes:
>
>> Hi,
>>
>> I'm encountering a compile-time error when building the latest Emacs igc branch with the `--with-mps=yes' and `--with-xwidget' options:
>
> The good news it's easy to fix that particular error (add ".header");
> the bad news is that no one reported this before, so you'd be the first
> to test this combination.

> It's probably best to look over the xwidgets code to make sure it
> doesn't have any obvious problems before testing this combination.

I didn't read all of the file, but I checked the basic stuff, and it
seems to be fine.  It also built and didn't immediately crash Emacs, but
I don't think I know how to use xwidgets (I also had to fake a pkgconfig
file for some reason, and try three distros to get it to work at
all...)

No guarantees, but I pushed something.  I had to copy out of a docker
container so hopefully made the same changes on scratch/igc.

I'd be very interested to hear whether this survives some GC cycles (M-x
igc-stats; then hit "c" a few times) when xwidgets are in use.  If it
does, we can close this bug.

Pip