[clang] [clang] Reuse configured VFS for chained includes (PR #173288)

[Ben Langmuir via cfe-commits]

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@@ -124,7 +124,7 @@ clang::createChainedIncludesSource(CompilerInstance &CI,
 
     auto Clang = std::make_unique<CompilerInstance>(
         std::move(CInvok), CI.getPCHContainerOperations());
-    Clang->createVirtualFileSystem();
+    Clang->setVirtualFileSystem(CI.getVirtualFileSystemPtr());
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benlangmuir wrote:

This deserves a comment that it is valid because none of the changes to the invocation above impact the VFS (e.g. no -ivfsoverlay changes).

https://github.com/llvm/llvm-project/pull/173288