[Dependency Scanning] Use a standalone DependencyScanningFilesystem on the scanner, sharing a common status cache from Clang's dependency service cache

Author: artemcm

lib/DependencyScan/ModuleDependencyScanner.cpp

@@ -153,6 +153,15 @@ ModuleDependencyScanningWorker::ModuleDependencyScanningWorker(
   auto ClangModuleCachePath = getModuleCachePathFromClang(
       ScanASTContext.getClangModuleLoader()->getClangInstance());
   auto &FEOpts = ScanCompilerInvocation.getFrontendOptions();
+
+  // Configure the filesystem to use the same shared `stat` cache as the Clang
+  // worker uses.
+  auto DepFS =
+      new clang::tooling::dependencies::DependencyScanningWorkerFilesystem(
+          globalScanningService.ClangScanningService->getSharedCache(),
+          ScanASTContext.SourceMgr.getFileSystem());
+  ScanASTContext.SourceMgr.setFileSystem(DepFS);
+
   ModuleInterfaceLoaderOptions LoaderOpts(FEOpts);
   ScanningASTDelegate = std::make_unique<InterfaceSubContextDelegateImpl>(
       ScanASTContext.SourceMgr, &ScanASTContext.Diags,