[libc++] Require C++20 to build the benchmarks.
Some work-in-progress patches for the format header contain benchmarks.
The format header requires C++20 to build. This is a preparation to make
it easy to add these benchmarks.
Reviewed By: ldionne, #libc
Differential Revision: https://reviews.llvm.org/D96057
GitOrigin-RevId: 34acc91642440b8e4bad17acfdbb1314c8f2043e
diff --git a/docs/ReleaseNotes.rst b/docs/ReleaseNotes.rst
index 00ada48..d9302fe 100644
--- a/docs/ReleaseNotes.rst
+++ b/docs/ReleaseNotes.rst
@@ -43,4 +43,5 @@
API Changes
-----------
-- ...
+- Starting with libc++13 a C++20 capable compiler is required to build the
+ libc++ benchmarks.