Updating Visual Studio 2022 to 19.27 for LLVM/CMake build

Question

I'm running Visual Studio 2022 community edition on Windows 10, and trying to compile the latest version of Clang, and I get the following message:

-- Selecting Windows SDK version 10.0.19041.0 to target Windows 10.0.19042.
-- bolt project is disabled
-- clang project is enabled
-- clang-tools-extra project is disabled
-- compiler-rt project is disabled
-- cross-project-tests project is disabled
-- libc project is disabled
-- libclc project is disabled
-- libcxx project is disabled
-- libcxxabi project is disabled
-- libunwind project is disabled
-- lld project is disabled
-- lldb project is disabled
-- mlir project is disabled
-- openmp project is disabled
-- polly project is disabled
-- pstl project is disabled
-- flang project is disabled
CMake Error at cmake/modules/CheckCompilerVersion.cmake:44 (message):
  Host Visual Studio version should be at least 19.27 because LLVM will soon
  use new C++ features which your toolchain version doesn't support.  Your
  version is 19.25.28610.4.  You can temporarily opt out using
  LLVM_TEMPORARILY_ALLOW_OLD_TOOLCHAIN, but very soon your toolchain won't be
  supported.
  

Okay, fair enough, I tell Visual Studio to update itself, it goes through the routine of downloading and installing a couple gigabytes of stuff, seems happy enough, I open a new command prompt, rerun

C:\Program Files\Microsoft Visual Studio\2022\Community\VC\Auxiliary\Build\vcvars64.bat

which also seems happy, and I try again to build Clang...

And get the same error message.

How do you get Visual Studio 2022 to update itself to 19.27, whatever that may be?

Alternatively, am I barking up the wrong tree? Is it the case that there is nothing wrong with the Visual Studio version at all, and the error message is actually a symptom of a completely different problem?