rr-unstable: 2020-10-04 -> 2021-07-06

It seems like the original reason for the rr-unstable package has gone
stale, and there has been a proper release (5.4.0) since it was made.
However, it has now been over 8 months since a release again, so I
figured I would repurpose rr-unstable.

I personally need the following unreleased commit to be able to use rr
at all on an AMD Ryzen 5900X CPU:

854b51effa

pkgs/development/tools/analysis/rr/unstable.nix

@@ -1,9 +1,8 @@
-# This is a temporary copy of the default.nix in this folder, with the version updated to the current tip of rr's master branch.
-# This exists because rr has not had a release in a long time, but there have been a lot of improvements including UX.
-# Some of the UX improvements help prevent foot shooting.
-# Upstream has stated that it should be fine to use master.
-# This file, and its attribute in all-packages, can be removed once rr makes a release.
-# For further information, please see https://github.com/NixOS/nixpkgs/issues/99535 "Improve support for the rr debugger in nixos containers"
+# This is a temporary copy of the default.nix in this folder, with the version
+# updated to the current tip of rr's master branch. This exists because rr has
+# not had a release in a long time. Upstream has stated that it should be fine
+# to use master. This file, and its attribute in all-packages, can be removed
+# once rr makes a release.
 
 { callPackage, fetchFromGitHub }:
 
@@ -12,12 +11,12 @@ let
 in
 
   rr.overrideAttrs (old: {
-    version = "unstable-2020-10-04";
+    version = "unstable-2021-07-06";
 
     src = fetchFromGitHub {
       owner = "mozilla";
       repo = "rr";
-      rev = "9ff375813a740a0a6ebcdfcebc58bd61ab68c667";
-      sha256 = "0raifs6cg5ckpi2445inhy3hfhp4p89s1lkx9z17mcc2g1c1phf5";
+      rev = "0fc21a8d654dabc7fb1991d76343824cb7951ea0";
+      sha256 = "0s851rflxmvxcfw97zmplcwzhv86xmd3my78pi4c7gkj18d621i5";
     };
   })