[clang] [llvm] [mlir] [support] Use VFS in `SourceMgr` for loading includes (PR #162903)

[Jan Svoboda via cfe-commits]

jansvoboda11 wrote:

Thank you for the report. I'll take a look and will attempt a forward-fix and I'll revert in case I can't get that done by EOD.

https://github.com/llvm/llvm-project/pull/162903