[yaml2obj/elf-override-shsize.yaml] - An attemp to fix ppc64 bot.

Failture:
http://lab.llvm.org:8011/builders/clang-ppc64be-linux/builds/35670/steps/ninja%20check%201/logs/FAIL%3A%20LLVM%3A%3Aelf-override-shsize.yaml

Solution:
Change `od` tool invocation to print single bytes.

llvm-svn: 365772