GNU HURD can be considered (for now?) like a GNU/Linux

git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@190056 91177308-0d34-0410-b5e6-96231b3b80d8
sysctl.h does not exist under GNU/HURD (like windows)

git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@190057 91177308-0d34-0410-b5e6-96231b3b80d8