[lldb] Fix a warning

This patch fixes:

  lldb/include/lldb/Symbol/Function.h:270:3: error:
  'lldb_private::CallEdge' has virtual functions but non-virtual
  destructor [-Werror,-Wnon-virtual-dtor]

Author: kazutakahirata

lldb/include/lldb/Symbol/Function.h

@@ -267,7 +267,7 @@ using CallSiteParameterArray = llvm::SmallVector<CallSiteParameter, 0>;
 class CallEdge {
 public:
   enum class AddrType : uint8_t { Call, AfterCall };
-  ~CallEdge();
+  virtual ~CallEdge();
 
   /// Get the callee's definition.
   ///