[libcxx-commits] [libcxx] [RFC][libc++] Install modules. (PR #75741)

[Louis Dionne via libcxx-commits]

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@@ -424,6 +428,8 @@ set(LIBCXX_INSTALL_INCLUDE_DIR "${CMAKE_INSTALL_INCLUDEDIR}/c++/v1" CACHE STRING
     "Path where target-agnostic libc++ headers should be installed.")
 set(LIBCXX_INSTALL_RUNTIME_DIR "${CMAKE_INSTALL_BINDIR}" CACHE STRING
     "Path where built libc++ runtime libraries should be installed.")
+set(LIBCXX_INSTALL_MODULE_DIR "${CMAKE_INSTALL_INCLUDEDIR}/../modules/c++/v1" CACHE STRING
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ldionne wrote:

Suggestions from our live review just now:

```
$prefix/usr/include/c++/v1/__private_modules/
$prefix/usr/modules/c++/v1/
$prefix/usr/share/libc++/v1/ (or whatever was agreed upon on the Discourse RFC)
$prefix/usr/share/c++/v1/
```

https://github.com/llvm/llvm-project/pull/75741