[Buildroot] [External] - Arm cortex-a55 problem when building busybox

[Nick Betteridge]

Hi Vincent,

> Without a defconfig with which to reproduce, it's hard to say for sure, but it seems like
> your compiler does not support `-mcpu=cortex-a55` which was added in GCC 8. There
> is a check in the Kconfig menu for this when building a BR toolchain. Are you using a
> custom toolchain perhaps?

Yes, I'm using gcc-linaro-7.3.1-2018.05-x86_64_aarch64-linux-gnu - so 
it's less than gcc 8! Excellent, thank you for pointing this out! I'll 
try using something more recent.

Best,

Nick