make yogaApple modular

Summary:
X-link: facebook/react-native#44938

Yoga is transitively included in Swift targets and needs to be modular.

Changelog: [Internal]

Reviewed By: NickGerleman

Differential Revision: D58469454

fbshipit-source-id: 72bc6b5d3e5ee0710d9334a626e4e7297ce26b09

Author: rmaz

yoga/YGMacros.h

@@ -35,6 +35,12 @@
 #define YG_EXPORT
 #endif
 
+#ifdef __OBJC__
+#if __has_include(<Foundation/Foundation.h>)
+#import <Foundation/Foundation.h>
+#endif
+#endif
+
 #ifdef NS_ENUM
 // Cannot use NSInteger as NSInteger has a different size than int (which is the
 // default type of a enum). Therefor when linking the Yoga C library into obj-c