Apple refers to "Mac OS X" as "macOS" now.

src/physfs_platform_macos.c

@@ -9,7 +9,7 @@
 #define __PHYSICSFS_INTERNAL__
 #include "physfs_internal.h"
 
-#ifdef PHYSFS_PLATFORM_MACOSX
+#ifdef PHYSFS_PLATFORM_MACOS
 
 #include <CoreFoundation/CoreFoundation.h>
 
@@ -212,7 +212,7 @@ char *__PHYSFS_platformCalcPrefDir(const char *org, const char *app)
     return retval;
 } /* __PHYSFS_platformCalcPrefDir */
 
-#endif /* PHYSFS_PLATFORM_MACOSX */
+#endif /* PHYSFS_PLATFORM_MACOS */
 
 /* end of physfs_platform_macos.c ... */
 

src/physfs_platforms.h

@@ -33,7 +33,7 @@
 #  if ((TARGET_IPHONE_SIMULATOR) || (TARGET_OS_IPHONE))
 #     define PHYSFS_NO_CDROM_SUPPORT 1
 #  endif
-#  define PHYSFS_PLATFORM_MACOSX 1
+#  define PHYSFS_PLATFORM_MACOS 1
 #  define PHYSFS_PLATFORM_POSIX 1
 #elif defined(macintosh)
 #  error Classic Mac OS support was dropped from PhysicsFS 2.0. Move to OS X.