bug#57420: 29.0.50; Failure configuring Emacs with animated WebP support

[Stefan Kangas]

Daniel Martín via "Bug reports for GNU Emacs, the Swiss army knife of
text editors" <bug-gnu-emacs@gnu.org> writes:

> I checked that the built Emacs has WebP support.
>
> What do you think? I'd need an build system expert to verify that this
> is TRT in GNU/Linux, Windows, or when pkg-config is not available.

FWIW, I tried building with that patch here (Debian GNU/Linux) and the
build doesn't have webp support.

    (image-type-available-p 'webp)
    => nil