Include comment about CONFIG_AV1_DECODER=0

Author: fdintino

.github/workflows/wheels-dependencies.sh

@@ -133,6 +133,8 @@ function build_libavif {
     fi
 
     local out_dir=$(fetch_unpack https://github.com/AOMediaCodec/libavif/archive/refs/tags/v$LIBAVIF_VERSION.tar.gz libavif-$LIBAVIF_VERSION.tar.gz)
+    # CONFIG_AV1_DECODER=0 is a flag for libaom (included as a subproject of
+    # libavif) to disable the compilation and inclusion of aom's AVIF decoder.
     (cd $out_dir \
         && CMAKE_POLICY_VERSION_MINIMUM=3.5 cmake \
             -DCMAKE_INSTALL_PREFIX=$BUILD_PREFIX \