diff -rupN --no-dereference libwebp-1.2.0/CMakeLists.txt libwebp-1.2.0-new/CMakeLists.txt

--- libwebp-1.2.0/CMakeLists.txt	2021-01-21 04:43:45.000000000 +0100

+++ libwebp-1.2.0-new/CMakeLists.txt	2021-02-01 11:37:20.760764115 +0100

@@ -506,8 +506,8 @@ endif()

 if(WEBP_BUILD_VWEBP)

   # vwebp

-  find_package(GLUT)

-  if(GLUT_FOUND)

+  find_package(FreeGLUT)

+  if(FreeGLUT_FOUND)

     include_directories(${WEBP_DEP_IMG_INCLUDE_DIRS})

     parse_makefile_am(${CMAKE_CURRENT_SOURCE_DIR}/examples "VWEBP_SRCS" "vwebp")

     add_executable(vwebp ${VWEBP_SRCS})

diff -rupN --no-dereference libwebp-1.2.0/examples/vwebp.c libwebp-1.2.0-new/examples/vwebp.c

--- libwebp-1.2.0/examples/vwebp.c	2021-01-21 04:43:45.000000000 +0100

+++ libwebp-1.2.0-new/examples/vwebp.c	2021-02-01 11:37:20.760764115 +0100

@@ -27,7 +27,7 @@

 #if defined(HAVE_GLUT_GLUT_H)

 #include <GLUT/glut.h>

 #else

-#include <GL/glut.h>

+#include <GL/freeglut.h>

 #ifdef FREEGLUT

 #include <GL/freeglut.h>

 #endif