Cygwin: Add release message for recent pipe fixes

Signed-off-by: Takashi Yano <[email protected]>
(cherry picked from commit 41104f60e72f8fa3cf81863aa51e87d97039c68d)

Author: tyan0

winsup/cygwin/release/3.6.4

@@ -15,3 +15,9 @@ Fixes:
 
 - Fix handling of invalid 4 byte UTF-8 sequences.
   Addresses: https://cygwin.com/pipermail/cygwin/2025-June/258358.html
+
+- Fix SSH hang with non-cygwin pipe reader.
+  Addresses: https://github.com/git-for-windows/git/issues/5682
+
+- Fix unexpected blocking mode change by pipe_data_available()
+  Addresses: https://github.com/git-for-windows/git/issues/5682#issuecomment-2997428207