[Courgette] Reduce AssemblyProgram to reduce Courgette-apply RAM floor and disk churn.

courgette/instruction_utils.h

Index: courgette/instruction_utils.h
diff --git a/courgette/instruction_utils.h b/courgette/instruction_utils.h
index d7dfe97e46625d24e61cb6fffbd44c68adbea9f2..df12aa6e23979b8aa178c326d3c48e8a1f82ecc1 100644
--- a/courgette/instruction_utils.h
+++ b/courgette/instruction_utils.h
@@ -61,6 +61,20 @@ class InstructionReceptor {
 // true on success, and false otherwise.
 using InstructionGenerator = base::Callback<CheckBool(InstructionReceptor*)>;
 
+// A counter that increments via .push_back(), so it can be passed via template
+// to substitute std::vector<T>, to count elements instead of storing them.
+template <typename T>
+class CountingVector {
+ public:
+  CountingVector() {}
+
+  void push_back(const T& /* unused */) { ++size_; }
+  size_t size() const { return size_; }
+
+ private:
+  size_t size_ = 0;
+};
+
 }  // namespace courgette
 
 #endif  // COURGETTE_INSTRUCTION_UTILS_H_