bug#61988: error compiling emacs

[Eli Zaretskii]

> From: "Ugo Tomei" <utomei@tiscali.it>
> Cc: <luangruo@yahoo.com>,
>       <61988@debbugs.gnu.org>
> Date: Tue, 7 Mar 2023 17:44:26 +0100
> 
> In the emacs dir I see config.log:
> 
> configure:14159: checking for libwebpdemux >= 0.6.0
> configure:14323: gcc -o conftest  -g3 -O2 -pthread -isystem
> /usr/include/librsvg-2.0 -isystem /usr/include/gdk-pixbuf-2.0 -isystem
> /usr/include/x86_64-linux-gnu -isystem /usr/include/libmount -isystem
> /usr/include/blkid -isystem /usr/include/cairo -isystem
> /usr/include/glib-2.0 -isystem /usr/lib/x86_64-linux-gnu/glib-2.0/include
> -isystem /usr/include/pixman-1 -isystem /usr/include/uuid -isystem
> /usr/include/freetype2 -isystem /usr/include/libpng16 -isystem
> /usr/include/webp       conftest.c -lsqlite3  -lsqlite3 -lX11   >&5
> | #define HAVE_WEBP 1
> pkg_cv_WEBP_CFLAGS=-I/usr/include/webp
> WEBP_CFLAGS='-isystem /usr/include/webp'
> WEBP_LIBS='-lwebpdemux'
> 
> I attached the log.
> [...]
> configure:14159: checking for libwebpdemux >= 0.6.0
> configure:14166: $PKG_CONFIG --exists --print-errors "$WEBP_MODULE"
> configure:14169: $? = 0
> configure:14183: $PKG_CONFIG --exists --print-errors "$WEBP_MODULE"
> configure:14186: $? = 0
> configure:14224: result: yes

I'm stumped: why doesn't it test WebPGetInfo?  Po Lu, do you
understand what happened here?