do not rerun ./configure causing FTCBFS with newer autotools-dev

do not rerun ./configure causing FTCBFS with newer autotools-dev

If the config.{sub,guess} files we linked in were newer than our
configure script we ended up recreating configure and then rerun it
without all the configuration options which were (potentially) present
for a previous run.

We avoid this by changing to the same ruleset as in the debian/rules
file which compares the config.* files against a stamp file rather than
the configure script itself as its the configuration itself which
depends on all scripts, not configure on the config scripts.

While at it, we also drop the 'make -s dirs' call as we don't need to do
it explicitly here as proper dependencies will take care of it.

Thanks: Helmut Grohne for the detailed bugreport.
Closes: 804923