LTO: wild: error: Undefined symbol WebPFree, referenced by

[marxin]

Noticed while building the libwebp Gentoo package, could be reproduced locally with:

wget https://storage.googleapis.com/downloads.webmproject.org/releases/webp/libwebp-1.6.0.tar.gz
tar xvzf libwebp-1.6.0.tar.gz
cd libwebp*
CFLAGS="-flto=auto -fuse-ld=wild" ./configure
make VERBOSE=1 V=1
...
make[1]: Entering directory '/tmp/libwebp-1.6.0/examples'
/bin/sh ../libtool  --tag=CC   --mode=link gcc -fvisibility=hidden -Wall -Wdeclaration-after-statement -Wextra -Wfloat-conversion -Wformat -Wformat-nonliteral -Wformat -Wformat-security -Wmissing-declarations -Wmissing-prototypes -Wold-style-definition -Wshadow -Wstrict-prototypes -Wundef -Wunreachable-code -Wunused-but-set-variable -Wunused -Wvla -flto=auto -fuse-ld=wild    -o dwebp dwebp-dwebp.o libexample_util.la ../imageio/libimagedec.la ../imageio/libimageenc.la ../imageio/libimageio_util.la ../src/libwebp.la -L/usr/lib -lpng16 -ljpeg
libtool: link: gcc -fvisibility=hidden -Wall -Wdeclaration-after-statement -Wextra -Wfloat-conversion -Wformat -Wformat-nonliteral -Wformat -Wformat-security -Wmissing-declarations -Wmissing-prototypes -Wold-style-definition -Wshadow -Wstrict-prototypes -Wundef -Wunreachable-code -Wunused-but-set-variable -Wunused -Wvla -flto=auto -fuse-ld=wild -o .libs/dwebp dwebp-dwebp.o  ./.libs/libexample_util.a ../imageio/.libs/libimagedec.a /tmp/libwebp-1.6.0/src/demux/.libs/libwebpdemux.so /tmp/libwebp-1.6.0/src/.libs/libwebp.so /tmp/libwebp-1.6.0/sharpyuv/.libs/libsharpyuv.so -lm ../imageio/.libs/libimageenc.a ../imageio/.libs/libimageio_util.a ../src/.libs/libwebp.so -L/usr/lib -lpng16 -ljpeg -Wl,-rpath -Wl,/usr/local/lib
wild: error: Undefined symbol WebPFree, referenced by
    /tmp/ccNZR24f.ltrans0.ltrans.o
collect2: error: ld returned 255 exit status