CMake: Fix FFmpeg find module

Uses find_package_handle_standard_args to handle the find_package call
from the root CMakeLists. Removes all the unnecessary logic after the
find_package and just sets it to REQUIRED.

CMakeLists.txt

@@ -458,22 +458,7 @@ if (UNIX AND NOT APPLE)
 endif()
 if (NOT YUZU_USE_BUNDLED_FFMPEG)
     # Use system installed FFmpeg
-    find_package(FFmpeg 4.3 QUIET COMPONENTS ${FFmpeg_COMPONENTS})
-
-    if (FFmpeg_FOUND)
-        # Overwrite aggregate defines from FFmpeg module to avoid over-linking libraries.
-        # Prevents shipping too many libraries with the AppImage.
-        set(FFmpeg_LIBRARIES "")
-        set(FFmpeg_INCLUDE_DIR "")
-
-        foreach(COMPONENT ${FFmpeg_COMPONENTS})
-            set(FFmpeg_LIBRARIES ${FFmpeg_LIBRARIES} ${FFmpeg_LIBRARY_${COMPONENT}} CACHE PATH "Paths to FFmpeg libraries" FORCE)
-            set(FFmpeg_INCLUDE_DIR ${FFmpeg_INCLUDE_DIR} ${FFmpeg_INCLUDE_${COMPONENT}} CACHE PATH "Path to FFmpeg headers" FORCE)
-        endforeach()
-    else()
-        message(WARNING "FFmpeg not found or too old, falling back to externals")
-        set(YUZU_USE_BUNDLED_FFMPEG ON)
-    endif()
+    find_package(FFmpeg 4.3 REQUIRED QUIET COMPONENTS ${FFmpeg_COMPONENTS})
 endif()
 
 # Prefer the -pthread flag on Linux.

externals/find-modules/FindFFmpeg.cmake

@@ -185,3 +185,11 @@ foreach(c ${_FFmpeg_ALL_COMPONENTS})
 endforeach()
 unset(_FFmpeg_ALL_COMPONENTS)
 unset(_FFmpeg_REQUIRED_VARS)
+
+include(FindPackageHandleStandardArgs)
+find_package_handle_standard_args(FFmpeg
+  REQUIRED_VARS
+    FFmpeg_LIBRARIES
+    FFmpeg_INCLUDE_DIR
+  HANDLE_COMPONENTS
+)