I discovered the dependency directive some time ago, and filed a doc bug.

It appears to be only for Android, ARM and iOS platforms only.

Here's a usage of it in the Delphi RTL:

function DBXLoader_GetDriver(Count: Longint; Names: TWideStringArray;  Values: TWideStringArray; ErrorMessage: TDBXWideStringBuilder; out pDriver: TDBXDriverHandle): TDBXErrorCode; cdecl; external LibName name 'DBXLoader_GetDriver' dependency VendorLib, LibCPP, VendorLibDep;