snappy: restore of RTTI patch

This is required for *Ceph* to compile, as the comment states, and was accidentally removed.
A similar patch is also present for *leveldb* for instance.
Also bumps the patch to the appropriate version.

partial revert of 5240499fb6

Signed-off-by: benaryorg <binary@benary.org>

pkgs/by-name/sn/snappy/package.nix

@@ -3,6 +3,7 @@
   stdenv,
   fetchFromGitHub,
   cmake,
+  fetchpatch,
   static ? stdenv.hostPlatform.isStatic,
 }:
 
@@ -19,6 +20,22 @@ stdenv.mkDerivation rec {
 
   patches = [
     ./revert-PUBLIC.patch
+    # Re-enable RTTI, without which other applications can't subclass snappy::Source
+    # While the patch was rejected upstream, it does not make it any less necessary to carry forward.
+    # ==> lack of RTTI *breaks* Ceph (and others) <==
+    #
+    # https://tracker.ceph.com/issues/53060
+    # https://build.opensuse.org/package/show/openSUSE:Factory/snappy
+    #
+    # Should this patch fail to apply use the above site to get the updated patch (rev in the url below).
+    # On the page there's a "latest revision" section which lists the last request which was merged into it.
+    # Click the "Request <insert number>" link, then view any file using "View file", and copy the rev from your address bar.
+    # For a different revision (in case nixpkgs is behind or something) you can go through the full revision history.
+    # Should the patch not be available for the nixpkgs version, ideally wait until the patch becomes available before bumping, or vendor it if necessary.
+    (fetchpatch {
+      url = "https://build.opensuse.org/public/source/openSUSE:Factory/snappy/reenable-rtti.patch?rev=e3449869b466869fc6b8a03a1a528fa6";
+      hash = "sha256-JhVhkHh7XPx1Bzf5xnOgWLgwh1oihX3O+emQWzE4Dho=";
+    })
   ];
 
   outputs = [