for Oleksiy Vyalov - Redirect stdin, stdout and stderr to /dev/null when launching LLGS process. Differential Revision: http://reviews.llvm.org/D6105

git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@221324 91177308-0d34-0410-b5e6-96231b3b80d8