Add thumbnail support via ffmpeg API (incomplete

extensions/cmake/FindAVUTIL.cmake

@@ -0,0 +1,33 @@
+find_package(PkgConfig)
+if (PkgConfig_FOUND)
+    pkg_check_modules(PC_AVUTIL QUIET IMPORTED_TARGET GLOBAL libavutil)
+endif()
+
+if (PC_AVUTIL_FOUND)
+    set(AVUTIL_FOUND TRUE)
+    set(AVUTIL_VERSION ${PC_AVUTIL_VERSION})
+    set(AVUTIL_VERSION_STRING ${PC_AVUTIL_STRING})
+    set(AVUTIL_LIBRARYS ${PC_AVUTIL_LIBRARIES})
+    if (USE_STATIC_LIBS)
+        set(AVUTIL_INCLUDE_DIRS ${PC_AVUTIL_STATIC_INCLUDE_DIRS})
+    else()
+        set(AVUTIL_INCLUDE_DIRS ${PC_AVUTIL_INCLUDE_DIRS})
+    endif()
+    if (NOT AVUTIL_INCLUDE_DIRS)
+        find_path(AVUTIL_INCLUDE_DIRS NAMES libavutil/avutil.h)
+    endif()
+    if (NOT TARGET AVUTIL::AVUTIL)
+        add_library(AVUTIL::AVUTIL ALIAS PkgConfig::PC_AVUTIL)
+    endif()
+else()
+    message(FATAL_ERROR "failed.")
+endif()
+
+include(FindPackageHandleStandardArgs)
+find_package_handle_standard_args(AVUTIL
+    FOUND_VAR AVUTIL_FOUND
+    REQUIRED_VARS
+        AVUTIL_LIBRARYS
+        AVUTIL_INCLUDE_DIRS
+    VERSION_VAR AVUTIL_VERSION
+)