autogen: compute short directories too

Not just short directory roots. The test suites did an improper
generator check and masked them as the generator masks were put in place
after the core development but before the autogen-specific logic tests
were created.

Source/cmLocalXCodeGenerator.h

@@ -30,7 +30,8 @@ public:
 
   ~cmLocalXCodeGenerator() override;
   std::string GetTargetDirectory(
-    cmGeneratorTarget const* target) const override;
+    cmGeneratorTarget const* target,
+    cmStateEnums::IntermediateDirKind kind) const override;
   void AppendFlagEscape(std::string& flags,
                         std::string const& rawFlag) const override;
   void Generate() override;