only for Win + non-ARM Linux - doesn't seem to be officially supported
in neither ARM nor macOS
configure.ac - require just SVT-JPEG-XS 0.9 as is in msys Win package
(proxy mode commented out - isn't needed to set to "proxy_mode_full"
explicitly, anyways)
current FFmpeg version dd2976b9 doesn't compile with SVT-AV1 commit
9485b939 with following error:
```
libavcodec/libsvtav1.c:240:14: error: ‘EbSvtAv1EncConfiguration’ has no member named ‘enable_adaptive_quantization’
240 | param->enable_adaptive_quantization = 0;
```
in similar fashion as already done for install_sdl.sh
As a bonus, we do not need to depend on whole prepare.sh for cache
rebuild but only on this script, which is perhaps cleaner and may
yield less rebuilds. Also prepare.sh is slightly easier.
added by the commit f3003ed1
For the original reason it is no longer needed (the higher bit depth
x264 is already included in distro repositories). Anyways, the version
of libx264, that will be installed, is taken from ppa:savoury1/vlc3,
anyways (newer one).
So use it (the `cmake --install` is perhaps better than make install
since it doesn't trigger rebuilds so often). Also to be consistent with
the other SVT compressions.
