[Buildroot] Autobuilder toolchain update: Blackfin and ARC

Hello,

FYI, I have rebuilt the Blackfin and ARC pre-built Buildroot toolchains
for the autobuilders. The changes are:

 * Rebuilt with 2016.08-rc2 + the Blackfin toolchain fixes + the uClibc
   ARC fix (runtime only, but since I was going to rebuild anyway)

 * C++ is now re-enabled for Blackfin with the Buildroot toolchain.

Thanks,

Thomas
-- 
Thomas Petazzoni, CTO, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com