slack: run preInstall & postInstall hooks

pkgs/applications/networking/instant-messengers/slack/default.nix

@@ -147,6 +147,8 @@ let
     dontPatchELF = true;
 
     installPhase = ''
+      runHook preInstall
+
       # The deb file contains a setuid binary, so 'dpkg -x' doesn't work here
       dpkg --fsys-tarfile $src | tar --extract
       rm -rf usr/share/lintian
@@ -172,6 +174,8 @@ let
       substituteInPlace $out/share/applications/slack.desktop \
         --replace /usr/bin/ $out/bin/ \
         --replace /usr/share/ $out/share/
+
+      runHook postInstall
     '';
   };
 
@@ -185,9 +189,11 @@ let
     sourceRoot = "Slack.app";
 
     installPhase = ''
+      runHook preInstall
       mkdir -p $out/Applications/Slack.app
       cp -R . $out/Applications/Slack.app
       /usr/bin/defaults write com.tinyspeck.slackmacgap SlackNoAutoUpdates -bool YES
+      runHook postInstall
     '';
   };
 in