Gentoo issue: https://bugs.gentoo.org/940915

diff '--color=auto' -Naur a/configure.ac b/configure.ac
--- a/configure.ac
+++ b/configure.ac
@@ -1843,13 +1843,13 @@
 can_import_avif=no
 can_export_avif=no
 if test "x$have_libheif" = xyes; then
-  can_import_heic=`$PKG_CONFIG --variable=builtin_h265_decoder libheif`
-  can_export_heic=`$PKG_CONFIG --variable=builtin_h265_encoder libheif`
+  can_import_heic=yes
+  can_export_heic=yes
   if test "x$can_import_heic" = xyes; then
     MIME_TYPES="$MIME_TYPES;image/heif;image/heic"
   fi
-  can_import_avif=`$PKG_CONFIG --variable=builtin_avif_decoder libheif`
-  can_export_avif=`$PKG_CONFIG --variable=builtin_avif_encoder libheif`
+  can_import_avif=yes
+  can_export_avif=yes
   if test "x$can_import_avif" = xyes; then
     MIME_TYPES="$MIME_TYPES;image/avif"
   fi