ADT::GenericCycleInfo: Hide validateTree() in -Asserts.

validateTree() is instantiated with __FILE__.
It will be pruned at link time due to -ffunction-sections but be left in
object files.
Its user is only GenericCycleInfo::compute() with assert(validateTree());
Therefore I think validateTree() may be hidden with NDEBUG.

This is a fixup for https://reviews.llvm.org/D112696

llvm/include/llvm/ADT/GenericCycleImpl.h

@@ -326,6 +326,7 @@ auto GenericCycleInfo<ContextT>::getCycle(const BlockT *Block) const
   return nullptr;
 }
 
+#ifndef NDEBUG
 /// \brief Validate the internal consistency of the cycle tree.
 ///
 /// Note that this does \em not check that cycles are really cycles in the CFG,
@@ -391,6 +392,7 @@ bool GenericCycleInfo<ContextT>::validateTree() const {
 
   return true;
 }
+#endif
 
 /// \brief Print the cycle info.
 template <typename ContextT>

llvm/include/llvm/ADT/GenericCycleInfo.h

@@ -249,7 +249,9 @@ public:
 
   /// Methods for debug and self-test.
   //@{
+#ifndef NDEBUG
   bool validateTree() const;
+#endif
   void print(raw_ostream &Out) const;
   void dump() const { print(dbgs()); }
   //@}