You may need to explicitly disable support for WebP:
./configure --without-webp
It looks like the libwebp installed in your case is old enough that its API
is incompatible with that used by Guacamole. I'd need to look deeper to
determine what the minimum version of libwebp would be for
Thought I would see how var I could get with installing Guacamole on a
Raspberry Pi. It was all looking so good, 'configure' gave me the thumbs up.
Alas 'make' failed compiling 'libguac_la-encode-webp.lo' with errors from
'encode-webp.c'.
Now I had to mess with the dependencies a little, falling