here is the part of my overlay that does this

      ghc964 =
        let
          override1 = super.haskell.compiler.ghc964.override {
            bootPkgs = self.haskell.packages.ghc963Binary;
          };
          override2 = override1.override {
            hadrian = override1.passthru.hadrian.overrideAttrs (oldAttrs: {
              patches = (oldAttrs.patches or [ ]) ++ [
                ./patches/hadrian-9.6.4-allow-Cabal-3.10.patch
                # https://gitlab.haskell.org/ghc/ghc/-/merge_requests/10714
                (super.fetchpatch {
                  url = "https://gitlab.haskell.org/ghc/ghc/-/commit/dd38aca95ac25adc9888083669b32ff551151259.patch";
                  hash = "sha256-xqs6mw/akxMy+XmVabACzsIviIKP4fS0UEgTk0HJcIc=";
                  stripLen = 1;
                })
              ];
            });
          };
        in
        override2.overrideAttrs (oldAttrs: {
          patches = (oldAttrs.patches or [ ]) ++ [
            # https://gitlab.haskell.org/ghc/ghc/-/merge_requests/12286
            (super.fetchpatch {
              url = "https://gitlab.haskell.org/ghc/ghc/-/commit/c5e47441ab2ee2568b5a913ce75809644ba83271.patch";
              hash = "sha256-t3KkuME6IqLWuESIMZ7OVAFu7s8G+x0ev+aVzBUqkhg=";
            })
          ];
        });