message: Xcode: warn about unguarded uses of new APIs
diff: CLANG_WARN_RANGE_LOOP_ANALYSIS = YES;
  CLANG_WARN_STRICT_PROTOTYPES = YES;
  CLANG_WARN_SUSPICIOUS_MOVE = YES;
  + CLANG_WARN_UNGUARDED_AVAILABILITY = YES_AGGRESSIVE;
  CLANG_WARN_UNREACHABLE_CODE = YES;
  CLANG_WARN__DUPLICATE_METHOD_MATCH = YES;
  COPY_PHASE_STRIP = NO;
  CLANG_WARN_RANGE_LOOP_ANALYSIS = YES;
  CLANG_WARN_STRICT_PROTOTYPES = YES;
  CLANG_WARN_SUSPICIOUS_MOVE = YES;
  + CLANG_WARN_UNGUARDED_AVAILABILITY = YES_AGGRESSIVE;
  CLANG_WARN_UNREACHABLE_CODE = YES;
  CLANG_WARN__DUPLICATE_METHOD_MATCH = YES;
  COPY_PHASE_STRIP = YES;
  