Replace use of stdenv.shell by runtimeShell

(cherry picked from commit eb1b86a5ec)

modules/home-environment.nix

@@ -370,7 +370,7 @@ in
         + optionalString (!cfg.emptyActivationPath) "\${PATH:+:}$PATH";
 
         activationScript = pkgs.writeScript "activation-script" ''
-          #!${pkgs.stdenv.shell}
+          #!${pkgs.runtimeShell}
 
           set -eu
           set -o pipefail

modules/programs/notmuch.nix

@@ -188,7 +188,7 @@ in
           {
             target = "${notmuchIni.database.path}/.notmuch/hooks/${name}";
             source = pkgs.writeScript name ''
-              #!${pkgs.stdenv.shell}
+              #!${pkgs.runtimeShell}
 
               export PATH="${pkgs.notmuch}/bin''${PATH:+:}$PATH"
               export NOTMUCH_CONFIG="${config.xdg.configHome}/notmuch/notmuchrc"

modules/services/emacs.nix

@@ -35,7 +35,7 @@ in
       };
 
       Service = {
-        ExecStart = "${pkgs.stdenv.shell} -l -c 'exec ${emacsBinPath}/emacs --fg-daemon'";
+        ExecStart = "${pkgs.runtimeShell} -l -c 'exec ${emacsBinPath}/emacs --fg-daemon'";
         ExecStop = "${emacsBinPath}/emacsclient --eval '(kill-emacs)'";
         Restart = "on-failure";
       };

nixos/default.nix

@@ -86,7 +86,7 @@ in
             # The activation script is run by a login shell to make sure
             # that the user is given a sane Nix environment.
             ExecStart = pkgs.writeScript "activate-${username}" ''
-              #! ${pkgs.stdenv.shell} -el
+              #! ${pkgs.runtimeShell} -el
               echo Activating home-manager configuration for ${username}
               exec ${usercfg.home.activationPackage}/activate
             '';