Fix Windows build when python is not explicitly enabled

Currently Windows disables Python builds by default.  This
change ensures we don't process the scripts dir when we're
on Windows unless we're explicitly enabling python, which
prevents a build error.

Change by Deepak Panickal


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@212319 91177308-0d34-0410-b5e6-96231b3b80d8