[analyzer] Add missing include to Z3Solver.cpp

Author: lukeshingles

llvm/lib/Support/Z3Solver.cpp

@@ -19,6 +19,7 @@ using namespace llvm;
 #include "llvm/ADT/Twine.h"
 
 #include <set>
+#include <unordered_map>
 
 #include <z3.h>