fix fmv greenscreens when CPU video decoding is enabled (#131)

This just reverts FFmpeg to 6.0.2 (known working version) but we should
probably take a look at what breaking changes occurred since then.

Signed-off-by: swurl <swurl@swurl.xyz>

Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/131
Co-authored-by: swurl <swurl@swurl.xyz>
Co-committed-by: swurl <swurl@swurl.xyz>

externals/ffmpeg/CMakeLists.txt

@@ -32,6 +32,7 @@ if (NOT WIN32 AND NOT ANDROID)
     endif()
 
     unset(FFmpeg_LIBRARIES CACHE)
+
     foreach(COMPONENT ${FFmpeg_COMPONENTS})
         set(FFmpeg_${COMPONENT}_PREFIX "${FFmpeg_BUILD_DIR}/lib${COMPONENT}")
         set(FFmpeg_${COMPONENT}_LIB_NAME "lib${COMPONENT}.a")