Support hidl_package_root require_frozen.

To help those maintain HIDL roots.

This property requires all referenced interfaces to be frozen.

Bug: 155593324
Test: manually checking that this works + hidl_hash_test
Change-Id: I4ce4bda54598a3e0cd13ab692d9defcbd089585b
diff --git a/Coordinator.h b/Coordinator.h
index 7715e56..766a806 100644
--- a/Coordinator.h
+++ b/Coordinator.h
@@ -42,6 +42,8 @@
     void setVerbose(bool value);
     bool isVerbose() const;
 
+    void setRequireFrozen(bool requireFrozen);
+
     void setDepFile(const std::string& depFile);
 
     const std::string& getOwner() const;
@@ -189,6 +191,7 @@
 
     // hidl-gen options
     bool mVerbose = false;
+    bool mRequireFrozen = false;
     std::string mOwner;
 
     // cache to parse().