[clang] [clang][docs] Improve "Obtaining Clang" section (PR #71313)

[Jessica Clarke via cfe-commits]

================
@@ -22,8 +22,8 @@ started guide <https://llvm.org/docs/GettingStarted.html>`_.
 
 .. code-block:: console
 
-      cd ~/clang-llvm
-      git clone https://github.com/llvm/llvm-project.git
+      mkdir ~/clang-llvm && cd ~/clang-llvm
+      git clone https://github.com/llvm/llvm-project.git .
----------------
jrtc27 wrote:

Given the:
```
      cd ~/clang-llvm
      git clone git://cmake.org/stage/cmake.git
```
this isn't a good idea. Better to clone it to an llvm-project subdirectory (i.e. drop the .) and alter later steps.

https://github.com/llvm/llvm-project/pull/71313