bug#61988: error compiling emacs

[Eli Zaretskii <eliz@gnu.org>]

reopen 61988
thanks

> From: Po Lu <luangruo@yahoo.com>
> Cc: utomei@tiscali.it,  61988-done@debbugs.gnu.org
> Date: Mon, 06 Mar 2023 21:43:06 +0800
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> >> From: Po Lu <luangruo@yahoo.com>
> >> Cc: 61988@debbugs.gnu.org, Eli Zaretskii <eliz@gnu.org>
> >> Date: Mon, 06 Mar 2023 18:35:05 +0800
> >> 
> >> >> -      WEBP_MODULE="libwebpdemux >= $WEBP_REQUIRED"
> >> >> +      WEBP_MODULE="libwebpdemux >= $WEBP_REQUIRED libwebpdecoder >= $WEBP_REQUIRED"
> >> >>           EMACS_CHECK_MODULES([WEBP], [$WEBP_MODULE])
> >> >>         AC_SUBST([WEBP_CFLAGS])
> >> >>
> >> >> Everyone else, make sure to link to *EVERYTHING* that you depend on, not
> >> >> just one library that happens to link to everything you depend on.
> >> >> Thanks.
> >> 
> >> Thanks.  Eli, is this safe for Emacs 29?
> >
> > Yes, thanks.
> 
> Thanks, I installed the patch and am closing this bug.

Sorry, I wasn't paying close attention, and though that you are adding
libwebpdemux.  With linwebpdecoder, the test fails on my system, since
libwebpdecoder is not installed and neither is its pkg-config file.
And is not needed: we don't use any API from that library, AFAICT.

So I've reverted that change for now, and I'm reopening the bug.

I'd like to know why requiring libwebpdecoder is essential for the
build to work on the OP's system.  It isn't on mine, and if you look
at init_webp_functions, you will see that on Windows we load functions
only from libwebp and libwebpdemux.  Why is the third library needed?