xbps-src: set XBPS_CACHEDIR in conf file for chroot ops.

xbps-src/shutils/chroot.sh.in

@@ -90,6 +90,10 @@ fi
 if [ -n "$XBPS_COMPRESS_LEVEL" ]; then
 	echo "XBPS_COMPRESS_LEVEL=$XBPS_COMPRESS_LEVEL" >> $XBPSSRC_CF
 fi
+if [ -n "$XBPS_CACHEDIR" ]; then
+	echo "XBPS_CACHEDIR=$XBPS_CACHEDIR" >> $XBPSSRC_CF
+fi
+
 echo "# End of configuration file." >> $XBPSSRC_CF
 
 if [ -d $XBPS_MASTERDIR/tmp ]; then