[Xcode] Add GTEST_NO_LLVM_RAW_OSTREAM declarations for Xcode project.
[Xcode] Add GTEST_NO_LLVM_RAW_OSTREAM declarations for Xcode project.

 - <rdar://problem/35299761> 2 errors in raw_os_ostream.h:33

apple/swift-llbuild,apple/swift-llbuild,apple/swift-llbuild,apple/swift-llbuild,apple/swift-llbuild,apple/swift-llbuild,apple/swift-llbuild