[analyzer] Add missing include <unordered_map> to llvm/lib/Support/Z3Solver.cpp (#106410)

Resolves #106361. Adding #include <unordered_map> to
llvm/lib/Support/Z3Solver.cpp fixes compilation errors for homebrew
build on macOS with Xcode 14.
https://github.com/Homebrew/homebrew-core/actions/runs/10604291631/job/29390993615?pr=181351
shows that this is resolved when the include is patched in (Linux CI
failure is due to unrelated timeout).

(cherry picked from commit fcb3a0485857c749d04ea234a8c3d629c62ab211)

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>