[libcxx] random_device, use arc4random() on Solaris

Reviewed By: ldionne

Differential Revision: https://reviews.llvm.org/D125068

NOKEYCHECK=True
GitOrigin-RevId: ed85de6db44e830b1019815d74aee1b595748b5d
diff --git a/docs/ReleaseNotes.rst b/docs/ReleaseNotes.rst
index 91a735c..cbbe6c0 100644
--- a/docs/ReleaseNotes.rst
+++ b/docs/ReleaseNotes.rst
@@ -104,8 +104,8 @@
   ``_LIBCPP_ABI_USE_CXX03_NULLPTR_EMULATION`` will not be honoured anymore and there
   will be no way to opt back into the C++03 emulation of ``std::nullptr_t``.
 
-- On FreeBSD, NetBSD and DragonFlyBSD, ``std::random_device`` is now implemented on top of
-  ``arc4random()`` instead of reading from ``/dev/urandom``. Any implementation-defined
+- On FreeBSD, NetBSD, DragonFlyBSD and Solaris, ``std::random_device`` is now implemented on
+  top of ``arc4random()`` instead of reading from ``/dev/urandom``. Any implementation-defined
   token used when constructing a ``std::random_device`` will now be ignored instead of
   interpreted as a file to read entropy from.