Fix Linux warning about missing virtual destructor in Operation classes

llvm-svn: 181712
diff --git a/lldb/source/Plugins/Process/Linux/ProcessMonitor.cpp b/lldb/source/Plugins/Process/Linux/ProcessMonitor.cpp
index e9a45d7..f7f7d8c 100644
--- a/lldb/source/Plugins/Process/Linux/ProcessMonitor.cpp
+++ b/lldb/source/Plugins/Process/Linux/ProcessMonitor.cpp
@@ -379,6 +379,7 @@
 class Operation
 {
 public:
+    virtual ~Operation() {}
     virtual void Execute(ProcessMonitor *monitor) = 0;
 };