remove the unnecessary libc build in build_deps.sh (#683)
remove the unnecessary libc build in build_deps.sh (#683)

The script build_deps.sh failed when building llvm/libc on freebsd. I found out that libc is not used in Souper, so I just removed it from build_deps.sh.
Test suite ran good on osx, ubuntu and freebsd for both debug and release for this patch.
google/souper,regehr/souper,jubitaneja/souper,google/souper,jubitaneja/souper,rsas/souper,rsas/souper,google/souper,jubitaneja/souper,regehr/souper,google/souper,regehr/souper,regehr/souper,rsas/souper,rsas/souper,jubitaneja/souper,rsas/souper,regehr/souper,rsas/souper,jubitaneja/souper,jubitaneja/souper,google/souper