[libcxx-commits] [libcxx] [libc++][doc] Updates module build instructions. (PR #89413)

[Louis Dionne via libcxx-commits]

================
@@ -214,6 +219,64 @@ Building this project is done with the following steps, assuming the files
 
              ``error: module file _deps/std-build/CMakeFiles/std.dir/std.pcm cannot be loaded due to a configuration mismatch with the current compilation [-Wmodule-file-config-mismatch]``
 
+
+Using the installed modules
+~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+CMake has added experimental support for importing the Standard modules. This
+is available in the current nightly builds and will be part of the 3.30
+release. Currently CMake only supports importing the Standard modules in C++23
+and later. Enabling this for C++20 is on the TODO list of the CMake
+developers.
+
+The example uses the same ``main.cpp`` as above. It uses the following
+``CMakeLists.txt``
+
+.. code-block:: cmake
+
+  # This requires a recent nightly build.
+  # This will be part of CMake 3.30.0.
+  cmake_minimum_required(VERSION 3.29.0 FATAL_ERROR)
+
+  # Enables the Standard module support. This needs to be done
+  # before selecting the languages.
+  set(CMAKE_EXPERIMENTAL_CXX_IMPORT_STD "0e5b6991-d74f-4b3d-a41c-cf096e0b2508")
+  set(CMAKE_CXX_MODULE_STD ON)
+
+  project("module"
----------------
ldionne wrote:

```suggestion
  project("example"
```

https://github.com/llvm/llvm-project/pull/89413