Fix comment and remove duplicated -Wno-sign-compare option.


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@217426 91177308-0d34-0410-b5e6-96231b3b80d8
Remove the -Wno-unused-function option. We are clean
with -Wunused-function as far as I can tell.


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@217428 91177308-0d34-0410-b5e6-96231b3b80d8