builddeb: ignore errors about find not finding files

The debuild command may output less files than we explicitly list so let's not
error out if none exist.

contrib/builddeb

@@ -84,7 +84,7 b' if [ "$CLEANUP" ] ; then'
     OUTPUTDIR=${OUTPUTDIR:=packages/$DISTID-$CODENAME}
     mkdir -p "$OUTPUTDIR"
     find ../mercurial*.deb ../mercurial_*.build ../mercurial_*.changes \
-          -type f -newer $control -print0 | \
+          -type f -newer $control -print0 2>/dev/null | \
       xargs -Inarf -0 mv narf "$OUTPUTDIR"
     echo "Built packages for $debver:"
     find "$OUTPUTDIR" -type f -newer $control -name '*.deb'