AlienBob's ffmpeg (restricted) SlackBuild error

Hi,

Using AlienBob's restricted SlackBuild for ffmpeg in Slackware -current it fails with this message:

Code:make[1]: Leaving directory '/tmp/build/tmp-ffmpeg/zvbi-0.2.35/po'
Making install in doc
make[1]: Entering directory '/tmp/build/tmp-ffmpeg/zvbi-0.2.35/doc'
make[2]: Entering directory '/tmp/build/tmp-ffmpeg/zvbi-0.2.35/doc'
make[2]: Nothing to be done for 'install-exec-am'.
make[2]: Nothing to be done for 'install-data-am'.
make[2]: Leaving directory '/tmp/build/tmp-ffmpeg/zvbi-0.2.35/doc'
make[1]: Leaving directory '/tmp/build/tmp-ffmpeg/zvbi-0.2.35/doc'
make[1]: Entering directory '/tmp/build/tmp-ffmpeg/zvbi-0.2.35'
make[2]: Entering directory '/tmp/build/tmp-ffmpeg/zvbi-0.2.35'
make[2]: Nothing to be done for 'install-exec-am'.
test -z "/tmp/build/tmp-ffmpeg/ffmpegdeps/usr/lib64/pkgconfig" || mkdir -p -- "/tmp/build/tmp-ffmpeg/ffmpegdeps/usr/lib64/pkgconfig"
/usr/bin/ginstall -c -m 644 'zvbi-0.2.pc' '/tmp/build/tmp-ffmpeg/ffmpegdeps/usr/lib64/pkgconfig/zvbi-0.2.pc'
make[2]: Leaving directory '/tmp/build/tmp-ffmpeg/zvbi-0.2.35'
make[1]: Leaving directory '/tmp/build/tmp-ffmpeg/zvbi-0.2.35'
/tmp/build/tmp-ffmpeg/dav1d-1.0.0/build
**
** ffmpeg ...
**
Hmm... Looks like a unified diff to me...
The text leading up to this was:
--------------------------
|diff '--color=auto' -rupN ffmpeg.orig/libavformat/avformat.h ffmpeg/libavformat/avformat.h
|--- ffmpeg.orig/libavformat/avformat.h 2022-08-19 17:42:47.323422603 +0200
|+++ ffmpeg/libavformat/avformat.h 2022-08-19 17:42:51.347130436 +0200
--------------------------
patching file libavformat/avformat.h
Using Plan A...
Hunk #1 succeeded at 1128.
Hmm... The next patch looks like a unified diff to me...
The text leading up to this was:
--------------------------
|diff '--color=auto' -rupN ffmpeg.orig/libavformat/mux_utils.c ffmpeg/libavformat/mux_utils.c
|--- ffmpeg.orig/libavformat/mux_utils.c 2022-08-19 17:42:47.346758108 +0200
|+++ ffmpeg/libavformat/mux_utils.c 2022-08-19 17:47:28.549589002 +0200
--------------------------
patching file libavformat/mux_utils.c
Using Plan A...
Hunk #1 succeeded at 37.
done
ERROR: libmfx not found

If you think configure made a mistake, make sure you are using the latest
version from Git. If the latest version fails, report the problem to the
ffmpeg-user@ffmpeg.org mailing list or IRC #ffmpeg on irc.libera.chat.
Include the log file "ffbuild/config.log" produced by configure as this will help
solve the problem.
Makefile:2: ffbuild/config.mak: No such file or directory
make: *** No rule to make target 'ffbuild/config.mak'. Stop.
Makefile:2: ffbuild/config.mak: No such file or directory
make: *** No rule to make target 'ffbuild/config.mak'. Stop.
** Adding ffmpeg presets:
** Fixing up pkgconfig files:
ls: cannot access '/tmp/build/package-ffmpeg/usr/lib64/pkgconfig/*.pc': No such file or directory
cp: cannot stat 'doc/*.html': No such file or directory
ffmpeg.SlackBuild FAILED at line 1909!But "mfx_dispatch library, for HW-accelerated playback on Intel GPUs" is in the sources directory of this SlackBuild and AFAIK it should be found.

Any ideas about what should I change? Has anybody else had this problem building this package?

Thank you,