MIPS builds on crochet

Hello Tim,

I'm using crochet to build simple MIPS images for my own test purposes and it is working really fine (building native images for now, it takes like 24 hours per image).

But on MIPS we use TARGET_CPUTYPE to select the ISA we want to build.

I'm using the attached patch to add it to my builds, can you take a look at it and check if this can be merged to crochet ? if you think it won't break anything else....

I hope i can look at cross building mips be images soon, but for now natives builds are working fine.

My board setup for mips is simple as:

TARGET_ARCH=mips
TARGET_CPUTYPE=mips32
KERNCONF=RSPRO
IMAGE_SIZE=$((500 * 1000 * 1000))

Thanks,
Luiz

Signed-off-by: Tim Kientzle <kientzle@acm.org>