Add Id GetBuiltInVariable(BuiltIn builtin) to spirv editor

Author: Zorro666

renderdoc/driver/shaders/spirv/spirv_editor.h

@@ -111,6 +111,7 @@ class Editor : public Processor
   void AddEntryGlobals(Id entry, const rdcarray<Id> &newGlobals);
   void ChangeEntry(Id from, Id to);
 
+  Id GetBuiltInVariable(BuiltIn builtin) { return builtinInputs[builtin].variable; }
   rdcpair<Id, Id> AddBuiltinInputLoad(OperationList &ops, ShaderStage stage, BuiltIn builtin,
                                       Id type);
   Id AddBuiltinInputLoad(OperationList &ops, rdcarray<Id> &addedGlobals, ShaderStage stage,