[clang] Load -fms-secure-hotpatch-functions-file= through the VFS (llvm#160146)

This PR uses the correctly-configured VFS to load the file specified via
`-fms-secure-hotpatch-functions-file=`, matching other input files of
the compiler.

Author: jansvoboda11

clang/lib/CodeGen/CodeGenModule.cpp

@@ -531,8 +531,7 @@ CodeGenModule::CodeGenModule(ASTContext &C,
   if (!CGO.MSSecureHotPatchFunctionsFile.empty() ||
       !CGO.MSSecureHotPatchFunctionsList.empty()) {
     if (!CGO.MSSecureHotPatchFunctionsFile.empty()) {
-      auto BufOrErr =
-          llvm::MemoryBuffer::getFile(CGO.MSSecureHotPatchFunctionsFile);
+      auto BufOrErr = FS->getBufferForFile(CGO.MSSecureHotPatchFunctionsFile);
       if (BufOrErr) {
         const llvm::MemoryBuffer &FileBuffer = **BufOrErr;
         for (llvm::line_iterator I(FileBuffer.getMemBufferRef(), true), E;