graphics/libavif: libjxl is linked if pkgconf is installed

From: Tatsuki Makino <>
Date: Thu, 11 Aug 2022 00:43:02 UTC

For libavif with option AOM enabled, libjxl may or may not be linked depending on whether or not pkgconf is installed.
This is because the variable _AOM_LDFLAGS in file ${WRKSRC}/cmake/Modules/Findaom.cmake of libavif changes.
The value of _AOM_LDFLAGS comes from `pkg-config --libs aom`, which includes -ljxl because the file /usr/local/libdata/pkgconfig/aom.pc contains "Requires: libjxl".

This may be a problem that requires changing libjxl to Requires.private on multimedia/aom side, not libavif.