Rewriting kernel config after generation

[Alexey Dobriyan <adobriyan@gmail.com>]

I'm trying to add compiling with -march=native to the kernel.
The problem is that then some config options become discoverable at
the beginning of the compilation. For example,
CONFIG_X86_L1_CACHE_SHIFT=6 can be derived from "--param l1-cache-line-size=64".
I suspect this is no-go, because all the dependency logic must be
duplicated somewhere else (in the march=native script) for the above
to work.

Is there any cleaner way I'm missing?

In theory, such script could even turn off CONFIG_CPU_SUP_AMD
if it detects Intel CPU.

	Alexey