[libc++] Do not install the C++ ABI library's headers as part of libc++'s build
It's the role of the C++ ABI library to install its own headers, not libc++.
This fixes an existing issue causing spurious CI failures where both libc++
and libc++abi would try to install <cxxabi.h> & friends in the same location,
leading to failures during the installation step.
Differential Revision: https://reviews.llvm.org/D121706
NOKEYCHECK=True
GitOrigin-RevId: 0389462587f8b89d6e724ccc4ff32d86963bfc22
diff --git a/docs/ReleaseNotes.rst b/docs/ReleaseNotes.rst
index d78549e..ce35d57 100644
--- a/docs/ReleaseNotes.rst
+++ b/docs/ReleaseNotes.rst
@@ -98,3 +98,11 @@
library should set ``LIBCXXABI_HERMETIC_STATIC_LIBRARY=ON`` when configuring CMake. The current
behavior, which tries to guess the correct dll-export semantics based on whether we're building
the libc++ shared library, will be removed in LLVM 16.
+
+- Previously, the C++ ABI library headers would be installed inside ``<prefix>/include/c++/v1``
+ alongside the libc++ headers as part of building libc++. This is not the case anymore -- the
+ ABI library is expected to install its headers where it wants them as part of its own build.
+ Note that no action is required for most users, who build libc++ against libc++abi, since
+ libc++abi already installs its headers in the right location. However, vendors building
+ libc++ against alternate ABI libraries should make sure that their ABI library installs
+ its own headers.