[Driver][Darwin] Disable default stack protector levels in freestanding mode.

Currently -fstack-protector is on by default when using -ffreestanding.
Change the default behavior to have it off when using -ffreestanding.

rdar://problem/14089363

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@288994 91177308-0d34-0410-b5e6-96231b3b80d8
(cherry picked from commit 74f707052af99f9ab9b2d6877e95e886517b5355)
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@289005 91177308-0d34-0410-b5e6-96231b3b80d8
(cherry picked from commit 267119fbb97e1d3ec80471bbe9ccbbbcf28fa676)
2 files changed