preinstallimage: Don't include files generated by build script

As these files may get provided by further packages to be installed
after the preinstall unpack. This leaded to a difference between
a system installed via preinstallimage, which is fixed now.

An example is the /etc/hosts file which is supposed to be created
by netcfg instead. build#848

init_buildsystem

@@ -1201,6 +1201,14 @@ test -c $BUILD_ROOT/dev/null || create_devs
 
 cd $BUILD_ROOT || cleanup_and_exit 1
 
+# exit early if we want to create a preinstall image
+if test -n "$CREATE_PREINSTALL_DATA" ; then
+    rm -rf "$BUILD_INIT_CACHE"
+    rm -f $BUILD_IS_RUNNING
+    rm -f $TMPFILE
+    cleanup_and_exit 0
+fi
+
 #
 # setup /etc/mtab
 #