plgx_local: Add cloog-0.18.0.tar.gz isl-0.11.1.tar.lzma tarballs

to git repo, save redownloading on every build / slave

Signed-off-by: David Holsgrove <david.holsgrove@xilinx.com>
samples: Update microblaze samples to default CT_CC_GCC_USE_GRAPHITE

Required by recent changes to ct-ng around default settings while
building gcc 4.8+

Signed-off-by: David Holsgrove <david.holsgrove@xilinx.com>