Driver: remove unused variable (NFC)
Driver: remove unused variable (NFC)

Remove `IsHosted` which is no longer needed in `RenderSSPOptions` after
SVN r312595.  The single use can now be inlined.  NFC

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@312616 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,llvm-mirror/clang,apple/swift-clang,apple/swift-clang,llvm-mirror/clang,llvm-mirror/clang,apple/swift-clang,llvm-mirror/clang,llvm-mirror/clang,apple/swift-clang,llvm-mirror/clang,apple/swift-clang,llvm-mirror/clang,apple/swift-clang,llvm-mirror/clang,apple/swift-clang,llvm-mirror/clang