Supporting multiple RN versions for new architecture in a library

[mfazekas]

Is there a way for libraries to support multiple RN versions with new architecture.
For example for rn 0.74 we'd had to add an extra param to LayoutMetrics. But I assume this will not build with 0.73 anymore.
Is there an #ifdef or something so we can support both 0.74 or 0.73 with the same library version?

 - (void)updateLayoutMetrics:(const LayoutMetrics &)layoutMetrics
           oldLayoutMetrics:(const LayoutMetrics &)oldLayoutMetrics
{
    CGRect prev = _view.frame;
    CGRect next = RCTCGRectFromRect(layoutMetrics.frame);
    
    BOOL frameDidChange = !CGRectEqualToRect(next, prev);
    if (frameDidChange) {
      next = CGRectMake(0, 0, next.size.width, next.size.height);
    }
    
    LayoutMetrics newLayoutMetrics = LayoutMetrics{
        RCTRectFromCGRect(next),
        layoutMetrics.contentInsets,
        layoutMetrics.borderWidth,
        layoutMetrics.displayType,
+        layoutMetrics.positionType, // RN074 
        layoutMetrics.layoutDirection,
        layoutMetrics.wasLeftAndRightSwapped,
        layoutMetrics.pointScaleFactor,
        

See also reactwg/react-native-releases#64 (comment)