Fix build with libheif >=1.18.0
See: https://github.com/strukturag/libheif/commit/cf0d89c6e0809427427583290547a7757428cf5a

Index: configure
--- configure.orig
+++ configure
@@ -30412,18 +30412,14 @@ $as_echo "yes" >&6; }
 fi
 fi
 
-can_import_heic=no
-can_export_heic=no
-can_import_avif=no
-can_export_avif=no
+can_import_heic=yes
+can_export_heic=yes
+can_import_avif=yes
+can_export_avif=yes
 if test "x$have_libheif" = xyes; then
-  can_import_heic=`$PKG_CONFIG --variable=builtin_h265_decoder libheif`
-  can_export_heic=`$PKG_CONFIG --variable=builtin_h265_encoder libheif`
   if test "x$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=`$PKG_CONFIG --variable=builtin_avif_encoder libheif`
   if test "x$can_import_avif" = xyes; then
     MIME_TYPES="$MIME_TYPES;image/avif"
   fi
