Retropie Setup does not work in Ubuntu 26.04

Description

I ran the retropie setup after upgrading from 24.10. It was a clean install. The set up script stops here. Hopefully there is an easy fix.

record/drivers/record_ffmpeg.c:375:25: error: ‘AV_INPUT_BUFFER_MIN_SIZE’ undeclared (first use in this function); did you mean ‘AV_INPUT_BUFFER_PADDING_SIZE’?
375 | audio->outbuf_size = AV_INPUT_BUFFER_MIN_SIZE;
| ^~~~~~~~~~~~~~~~~~~~~~~~
| AV_INPUT_BUFFER_PADDING_SIZE
record/drivers/record_ffmpeg.c:375:25: note: each undeclared identifier is reported only once for each function it appears in
CC gfx/video_crt_switch.c
record/drivers/record_ffmpeg.c: In function ‘ffmpeg_free’:
record/drivers/record_ffmpeg.c:952:7: error: implicit declaration of function ‘avcodec_close’; did you mean ‘avio_close’? [-Wimplicit-function-declaration]
952 | avcodec_close(handle->audio.codec);
| ^~~~~~~~~~~~~
| avio_close
make: *** [Makefile:209: obj-unix/release/record/drivers/record_ffmpeg.o] Error 1
make: *** Waiting for unfinished jobs....
cores/libretro-ffmpeg/ffmpeg_core.c: In function ‘libretro_ffmpeg_retro_unload_game’:
cores/libretro-ffmpeg/ffmpeg_core.c:2092:10: error: implicit declaration of function ‘avcodec_close’; did you mean ‘avcodec_license’? [-Wimplicit-function-declaration]
2092 | avcodec_close(sctx[i]);
| ^~~~~~~~~~~~~
| avcodec_license
make: *** [Makefile:207: obj-unix/release/cores/libretro-ffmpeg/ffmpeg_core.o] Error 1
Could not successfully build retroarch - RetroArch - frontend to the libretro emulator cores - required by all lr-* emulators (/home/bo/RetroPie-Setup/tmp/build/retroarch/retroarch not found).
/home/bo/RetroPie-Setup
Errors:
Could not successfully build retroarch - RetroArch - frontend to the libretro emulator cores - required by all lr-* emulators (/home/bo/RetroPie-Setup/tmp/build/retroarch/retroarch not found).

Start by reproducing the RetroArch build through the RetroPie setup on Ubuntu 26.04 and inspect the compiler errors in record/drivers/record_ffmpeg.c and cores/libretro-ffmpeg/ffmpeg_core.c. Done means RetroArch builds successfully and the setup can find its generated executable so the lr-* emulators continue installing.