[llvm] [docs][CMake] Add CMakePreset, improve VS documentation (PR #84760)

[Aaron Ballman via llvm-commits]

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@@ -72,7 +73,8 @@ These instruction were tested with Visual Studio 2019 and Python 3.9.6:
 1. Download and install `Visual Studio <https://visualstudio.microsoft.com/>`_.
 2. In the Visual Studio installer, Workloads tab, select the
    **Desktop development with C++** workload. Under Individual components tab,
-   select **Git for Windows**.
+   select **Git for Windows**. You might want to install **C++ Clang compiler for Windows**
+   as well, since this will allow you to build LLVM with Clang. 
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AaronBallman wrote:

```suggestion
   as well, since this will allow you to build LLVM with Clang.
```
Removes trailing whitespace.

https://github.com/llvm/llvm-project/pull/84760