Check for inputs not generated by deps

tools/gn/target.h

Index: tools/gn/target.h
diff --git a/tools/gn/target.h b/tools/gn/target.h
index 081f81ee2c64ab7712ed3c71da1898edf8fc0a78..3c569cccbe31e913e99e5d1ea11ef6e9d2df63fe 100644
--- a/tools/gn/target.h
+++ b/tools/gn/target.h
@@ -219,6 +219,16 @@ class Target : public Item {
   // frequently by unit tests which become needlessly verbose.
   bool SetToolchain(const Toolchain* toolchain, Err* err = nullptr);
 
+  // Once this target has been resolved, all outputs from the target will be
+  // listed here. This will include things listed in the "outputs" for an
+  // action or a copy step, and the output library or executable file(s) from
+  // binary targets.
+  //
+  // It will NOT include stamp files and object files.
+  const std::vector<OutputFile>& computed_outputs() const {
+    return computed_outputs_;
+  }
+
   // Returns outputs from this target. The link output file is the one that
   // other targets link to when they depend on this target. This will only be
   // valid for libraries and will be empty for all other target types.
@@ -258,6 +268,8 @@ class Target : public Item {
   bool CheckVisibility(Err* err) const;
   bool CheckTestonly(Err* err) const;
   bool CheckNoNestedStaticLibs(Err* err) const;
+  bool CheckSourcesGenerated(Err* err) const;
+  bool CheckSourceGenerated(const SourceFile& source, Err* err) const;
 
   OutputType output_type_;
   std::string output_name_;
@@ -302,7 +314,8 @@ class Target : public Item {
   // Toolchain used by this target. Null until target is resolved.
   const Toolchain* toolchain_;
 
-  // Output files. Null until the target is resolved.
+  // Output files. Empty until the target is resolved.
+  std::vector<OutputFile> computed_outputs_;
   OutputFile link_output_file_;
   OutputFile dependency_output_file_;