ci/mac: install ffmpeg-full with homebrew when available

homebrew slimmed down their ffmpeg formula and stripping it off some
essential functionality.

use ffmpeg-full instead when available. this is a new formula and not
available on older homebrew version. additionally, this is keg only
formula and not automatically symlinked system wide. make sure ffmpeg
is not installed in parallel and install ffmpeg-full system wide.

Author: Akemi

.github/workflows/build.yml

@@ -295,8 +295,15 @@ jobs:
           else
             brew update
           fi
+          if brew info ffmpeg-full &> /dev/null; then
+            brew install -q ffmpeg-full
+            brew unlink ffmpeg
+            brew link ffmpeg-full
+          else
+            brew install -q ffmpeg
+          fi
           brew install -q autoconf automake pkgconf libtool python freetype fribidi little-cms2 \
-            luajit libass ffmpeg meson rust uchardet mujs libplacebo molten-vk vulkan-loader vulkan-headers \
+            luajit libass meson rust uchardet mujs libplacebo molten-vk vulkan-loader vulkan-headers \
             libarchive libbluray libcaca libcdio-paranoia libdvdnav rubberband zimg
 
       - name: Build with meson