manual-config: Patch conf.c for generate-config.pl

This only affects the `oldaskconfig' make target, so it shouldn't really
affect current manual-config users, but it does make it more
straightforward to implement the generic kernel build on top of
manual-config.

Signed-off-by: Shea Levy <shea@shealevy.com>

pkgs/os-specific/linux/kernel/manual-config.nix

@@ -81,6 +81,10 @@ let
           sed -i "$mf" -e 's|/usr/bin/||g ; s|/bin/||g ; s|/sbin/||g'
       done
       sed -i Makefile -e 's|= depmod|= ${kmod}/sbin/depmod|'
+      # Patch kconfig to print "###" after every question so that
+      # generate-config.pl from the generic builder can answer them.
+      # This only affects oldaskconfig.
+      sed -e '/fflush(stdout);/i\printf("###");' -i scripts/kconfig/conf.c
     '';
 
     installPhase = ''