[clang][DepScan] Include -ivfsoverlay in the strict context hash

Include `-ivfsoverlay` in the strict context hash to avoid non-determinism in scanning.

Author: Bigcheese

clang/lib/Frontend/CompilerInvocation.cpp

@@ -5113,6 +5113,7 @@ std::string CompilerInvocation::getModuleHash(DiagnosticsEngine &Diags) const {
   if (hsOpts.ModulesStrictContextHash) {
     HBuilder.addRange(hsOpts.SystemHeaderPrefixes);
     HBuilder.addRange(hsOpts.UserEntries);
+    HBuilder.addRange(hsOpts.VFSOverlayFiles);
 
     const DiagnosticOptions &diagOpts = getDiagnosticOpts();
 #define DIAGOPT(Name, Bits, Default) HBuilder.add(diagOpts.Name);