[Cake] gcc 7.3.1 issue on arch

[Jonathan Morton]

> On 29 Mar, 2018, at 1:30 am, Bret Towe <bret.towe at gmail.com> wrote:
> 
> ./include/linux/kernel.h:6:10: fatal error: stdarg.h: No such file or directory

I've started seeing the same error on my PowerPC box, running Gentoo.  It seemed specific to that machine, but the GCC version may well be relevant since Gentoo tends to stabilise new GCC versions earlier on minority platforms.

Shouldn't stdarg.h be a built-in header?

 - Jonathan Morton