>  # actual new tmp installation
>  .tmp_install:
>     $(RM) ./.tmp_install.*
>     $(RM) -r ./tmp_install
>     # create tmp installation...
>     touch $@
>
>  # tmp installation for the nonce
>  .tmp_install.$(MAKE_NONCE): .tmp_install
>      touch $@
Oops, I got it wrong, the install would not be reexecuted the second time.
Maybe someting more like:
  ifdef USE_ONE_INSTALL  TMP_INSTALL = .tmp_install.once  else  TMP_INSTALL = .tmp_install.$(MAKE_NONCE)  endif
  $(TMP_INSTALL):      $(RM) -r ./tmp_install .tmp_install.*      # do installation...      touch $@
So that the file target is different each time it is run. Hopefully.
-- 
Fabien.