"./contrib/gcc_update --touch" doesn't work with make

[H. J. Lu]

./contrib/gcc_update has

    while ${MAKE-make} -f Makefile.$$ all | grep . > /dev/null; do
      sleep 1
    done 2>&1

It won't work at all if you run it inside a makefile. You will get

make[1]: Leaving directory `...'
make[1]: Entering directory `...'

instead of empty line. For gnu make, I think you can use 

    while ${MAKE-make} -s -f Makefile.$$ all | grep . > /dev/null; do


H.J.