config: fix CONFIG_GDB appearing in main menuconfig menu

config: fix CONFIG_GDB appearing in main menuconfig menu

I noticed that CONFIG_GDB was suddenly appearing in the main menuconfig
menu despite the fact that it should be visible only when TOOLCHAINOPTS
is selected and under a dedicated menu.

After some trial and error, it seems that this was caused by the recent
addition of GCC_USE_DEFAULT_VERSION, and after even more trial and error
it gets fixed as soon GCC_USE_DEFAULT_VERSION is placed after GCC_VERSION.

So, lets simply put GCC_USE_DEFAULT_VERSION after GCC_VERSION.

Fixes: 501ef81040ba ("config: select KERNEL_WERROR if building with default GCC version")
Signed-off-by: Robert Marko <robimarko@gmail.com>