llvm: Add missing VirtualFileSystem.h include (#171848)

`vfs::FileSystem` is forward-declared in `SanitizerBinaryMetadata.h`.
The corresponding header must be included in any source file that
includes that header, or we risk issues when building with
`LLVM_BUILD_LLVM_DYLIB` to build LLVM as a DLL on Windows.

This effort is tracked in #109483.

Author: Steelskin

llvm/lib/CodeGen/SanitizerBinaryMetadata.cpp

@@ -20,6 +20,7 @@
 #include "llvm/IR/MDBuilder.h"
 #include "llvm/InitializePasses.h"
 #include "llvm/Pass.h"
+#include "llvm/Support/VirtualFileSystem.h"
 #include "llvm/Transforms/Instrumentation/SanitizerBinaryMetadata.h"
 #include <algorithm>