package/motion: fix webp build

Fix the following build failure raised since bump of webp to version
1.3.2 in commit c88c1d3:

/home/autobuild/autobuild/instance-9/output-1/host/lib/gcc/aarch64_be-buildroot-linux-uclibc/13.2.0/../../../../aarch64_be-buildroot-linux-uclibc/bin/ld: picture.o: undefined reference to symbol 'WebPMemoryWriterClear'
/home/autobuild/autobuild/instance-9/output-1/host/lib/gcc/aarch64_be-buildroot-linux-uclibc/13.2.0/../../../../aarch64_be-buildroot-linux-uclibc/bin/ld: /home/autobuild/autobuild/instance-9/output-1/host/aarch64_be-buildroot-linux-uclibc/sysroot/usr/lib64/libwebp.so.7: error adding symbols: DSO missing from command line

Fixes:
 - http://autobuild.buildroot.org/results/9b859a701debeaddf1f9909e16adc6811a620576

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
(cherry picked from commit 1267a23)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/motion/0002-Include-libwebp-when-WEBP-is-enabled.patch

@@ -0,0 +1,26 @@
+From 40ecd71ff361442f1579089481619dd7cae90ffd Mon Sep 17 00:00:00 2001
+From: Piotr Mionskowski <piotr.mionskowski@gmail.com>
+Date: Sun, 9 Jul 2023 01:44:49 +0200
+Subject: [PATCH] Include libwebp when WEBP is enabled
+
+Upstream: https://github.com/Motion-Project/motion/commit/40ecd71ff361442f1579089481619dd7cae90ffd
+Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
+---
+ configure.ac | 4 ++--
+ 1 file changed, 2 insertions(+), 2 deletions(-)
+
+diff --git a/configure.ac b/configure.ac
+index ce588f65..ee45ac37 100644
+--- a/configure.ac
++++ b/configure.ac
+@@ -191,8 +191,8 @@ AS_IF([test "${WEBP}" = "yes" ], [
+     AS_IF([pkg-config libwebpmux ], [
+         AC_MSG_RESULT(yes)
+         AC_DEFINE([HAVE_WEBP], [1], [Define to 1 if WEBP is around])
+-        TEMP_CFLAGS="$TEMP_CFLAGS "`pkg-config --cflags libwebpmux`
+-        TEMP_LIBS="$TEMP_LIBS "`pkg-config --libs libwebpmux`
++        TEMP_CFLAGS="$TEMP_CFLAGS "`pkg-config --cflags libwebpmux libwebp`
++        TEMP_LIBS="$TEMP_LIBS "`pkg-config --libs libwebpmux libwebp`
+       ],[
+         AC_MSG_RESULT(no)
+       ]