Allows features to link to other feature splits without namespacing.

Add uses-split dependencies to AppInfo. At link time, this is used
and allows features to reference other features, before
resource namespacing is implemented in Android Studio.

bug:135681292
Test: Link_test, ReferenceLinker_test, and integration tests.
Change-Id: Ifdf0067e7370552b6b9d4d6d4713d4484b6ea154
diff --git a/tools/aapt2/cmd/Convert.cpp b/tools/aapt2/cmd/Convert.cpp
index 0cf86cc..22bcd85 100644
--- a/tools/aapt2/cmd/Convert.cpp
+++ b/tools/aapt2/cmd/Convert.cpp
@@ -243,6 +243,12 @@
     return 0u;
   }
 
+  const std::set<std::string>& GetSplitNameDependencies() override {
+    UNIMPLEMENTED(FATAL) << "Split Name Dependencies should not be necessary";
+    static std::set<std::string> empty;
+    return empty;
+  }
+
   bool verbose_ = false;
   std::string package_;