🍒 llvm: Add missing `VirtualFileSystem.h` include (llvm#171848)#12004

Steelskin wants to merge 1 commit intoswiftlang:stable/21.xswiftlang/llvm-project:stable/21.xfrom

Steelskin:fabrice/cp-include-virtual-filesystemSteelskin/llvm-project:fabrice/cp-include-virtual-filesystemCopy head branch name to clipboard