Use the function attributes to pass along the stack protector buffer size.

Use the function attributes to pass along the stack protector buffer size.

Now that we have robust function attributes, don't use a command line option to
specify the stack protecto buffer size.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@186217 91177308-0d34-0410-b5e6-96231b3b80d8