Add support for make nconfig

[DarthGandalf]

The following patch is a dirty hack, the proper support would probably involve adding --[no-]nconfig. But I don't understand interaction between different kinds of ...config.

diff --git a/gen_configkernel.sh b/gen_configkernel.sh
index 98b6e9c..e125873 100755
--- a/gen_configkernel.sh
+++ b/gen_configkernel.sh
@@ -83,7 +83,7 @@ config_kernel() {
    if isTrue ${MENUCONFIG}
    then
        print_info 1 'kernel: >> Invoking menuconfig...'
-       compile_generic menuconfig kernelruntask
+       compile_generic nconfig kernelruntask
        [ "$?" ] || gen_die 'Error: menuconfig failed!'
    elif isTrue ${CMD_GCONFIG}
    then