[poky] libc configuration of multilib config

[Jonathan Richardson]

Hi,

We have a cortex-A72 tuning defined as our default tuning based on armv8.
We also have some bare metal code that runs on a cortex M0. Yocto allows
you to set a default tune for that multilib config so we call it softfp
but it's an armv6 architecture with soft floating point:

MULTILIB_GLOBAL_VARIANTS += "softfp"
MULTILIBS += "multilib:softfp"
DEFAULTTUNE_virtclass-multilib-softfp = "armv6t-novfp"

Since we only have 1 recipe for code running on that processor (the SOC
contains armv8 and an M0) we compile it as softp-recipe_name, add it to
EXTRA_IMAGEDEPENDS along with other bootloaders and have everything in the
same deploy/machine when we create our image.

Now we want to use newlib instead of glibc for the softfp multilib config
only. I don't see a way of configuring this. At this point should we put
it in a different MACHINE? Are there any guidelines on when to use
multilib and when to put it in a new machine?

Thanks.