Update time on Haskell binaries after build

Update time on Haskell binaries after build

This patch works around an issue in our build system. Since we don't
use cabal or 'ghc -M', we don't track actual dependencies in our
Makefile; this in turn means that editing a file that only is used in
the main 'htools' binary will keep triggering 'ghc --make' for the
hconfd binary; and this actually takes a bit of time to look at all
the dependencies.

So to work around this, we add a touch after each ghc --make, such
that we trigger the unneeded build at most once.

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: René Nussbaumer <rn@google.com>