lli: Check pipe creation for errors.

This is unlikely to ever fail, but ubuntu GCC warns when the return value is
unused.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191973 91177308-0d34-0410-b5e6-96231b3b80d8
Temporarily revert r176882 as it needs to be implemented in a different
way for all platforms.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191975 91177308-0d34-0410-b5e6-96231b3b80d8