stdenv/setup.sh: Always run postPatch hook.

I'm not sure whether this was by intention, but so far postPatch hooks were
silently skipped whenever the patches list was empty. This change could possibly
change the build results of the following packages:

 * gcc
 * cmake (264)
 * systemtap
 * quemu-kvm

These packages all have in common that they have a postPatch hook and the
patches list can be empty when certain conditions are met.

Signed-off-by: aszlig <aszlig@redmoonstudios.org>
make: PATCHES from gentoo

also needed for updated firebird to build
gnumake: patch the patches so it looks nice
gnumake381: fix the patching because of gnumake