Merge pull request #9557 from swiftlang/jan_svoboda/share-fm-with-casfs

[clang][deps] Disable `FileManager` sharing with `CASFS`

Author: jansvoboda11

clang/lib/Tooling/DependencyScanning/DependencyScanningWorker.cpp

@@ -480,6 +480,8 @@ class DependencyScanningAction : public tooling::ToolAction {
     // This will prevent us compiling individual modules asynchronously since
     // FileManager is not thread-safe, but it does improve performance for now.
     ScanInstance.getFrontendOpts().ModulesShareFileManager = true;
+    if (DepCASFS)
+      ScanInstance.getFrontendOpts().ModulesShareFileManager = false;
     ScanInstance.getHeaderSearchOpts().ModuleFormat = "raw";
     ScanInstance.getHeaderSearchOpts().ModulesIncludeVFSUsage =
         any(OptimizeArgs & ScanningOptimizations::VFS);