signal-desktop: use autoPatchelfHook, wrap properly (#77850)

Most prominently we don't use `phases` because of https://github.com/NixOS/nixpkgs/issues/28910.
This is also problematic when using wrapGAppsHook.
In order to use wrapGAppsHook's automatic wrapping
(this was done manually before because there was no fixupPhase)
we need to install signal at lib/Signal instead of just into libexec.
That's because it would try to wrap .so files.

pkgs/applications/networking/instant-messengers/signal-desktop/default.nix

@@ -2,7 +2,8 @@
 , gnome2, gtk3, atk, at-spi2-atk, cairo, pango, gdk-pixbuf, glib, freetype, fontconfig
 , dbus, libX11, xorg, libXi, libXcursor, libXdamage, libXrandr, libXcomposite
 , libXext, libXfixes, libXrender, libXtst, libXScrnSaver, nss, nspr, alsaLib
-, cups, expat, udev, libnotify, libuuid, at-spi2-core, libappindicator-gtk3
+, cups, expat, systemd, libnotify, libuuid, at-spi2-core, libappindicator-gtk3
+, autoPatchelfHook
 # Unfortunately this also overwrites the UI language (not just the spell
 # checking language!):
 , hunspellDicts, spellcheckerLanguage ? null # E.g. "de_DE"
@@ -21,11 +22,32 @@ let
         --set HUNSPELL_DICTIONARIES "${hunspellDicts.${hunspellDict}}/share/hunspell" \
         --set LC_MESSAGES "${spellcheckerLanguage}"''
       else "");
-  rpath = lib.makeLibraryPath [
+in stdenv.mkDerivation rec {
+  pname = "signal-desktop";
+  version = "1.29.6"; # Please backport all updates to the stable channel.
+  # All releases have a limited lifetime and "expire" 90 days after the release.
+  # When releases "expire" the application becomes unusable until an update is
+  # applied. The expiration date for the current release can be extracted with:
+  # $ grep -a "^{\"buildExpiration" "${signal-desktop}/lib/Signal/resources/app.asar"
+  # (Alternatively we could try to patch the asar archive, but that requires a
+  # few additional steps and might not be the best idea.)
+
+  src = fetchurl {
+    url = "https://updates.signal.org/desktop/apt/pool/main/s/signal-desktop/signal-desktop_${version}_amd64.deb";
+    sha256 = "1s1rc4kyv0nxz5fy5ia7fflphf3izk80ks71q4wd67k1g9lvcw24";
+  };
+
+  nativeBuildInputs = [
+    autoPatchelfHook
+    dpkg
+    wrapGAppsHook
+  ];
+
+  buildInputs = [
     alsaLib
-    atk
     at-spi2-atk
     at-spi2-core
+    atk
     cairo
     cups
     dbus
@@ -36,10 +58,6 @@ let
     glib
     gnome2.GConf
     gtk3
-    pango
-    libappindicator-gtk3
-    libnotify
-    libuuid
     libX11
     libXScrnSaver
     libXcomposite
@@ -51,55 +69,42 @@ let
     libXrandr
     libXrender
     libXtst
+    libappindicator-gtk3
+    libnotify
+    libuuid
     nspr
     nss
-    udev
+    pango
+    systemd
     xorg.libxcb
   ];
 
-in stdenv.mkDerivation rec {
-  pname = "signal-desktop";
-  version = "1.29.6"; # Please backport all updates to the stable channel.
-  # All releases have a limited lifetime and "expire" 90 days after the release.
-  # When releases "expire" the application becomes unusable until an update is
-  # applied. The expiration date for the current release can be extracted with:
-  # $ grep -a "^{\"buildExpiration" "${signal-desktop}/libexec/resources/app.asar"
-  # (Alternatively we could try to patch the asar archive, but that requires a
-  # few additional steps and might not be the best idea.)
-
-  src = fetchurl {
-    url = "https://updates.signal.org/desktop/apt/pool/main/s/signal-desktop/signal-desktop_${version}_amd64.deb";
-    sha256 = "1s1rc4kyv0nxz5fy5ia7fflphf3izk80ks71q4wd67k1g9lvcw24";
-  };
-
-  phases = [ "unpackPhase" "installPhase" ];
-
-  nativeBuildInputs = [ dpkg wrapGAppsHook ];
+  runtimeDependencies = [
+    systemd.lib
+  ];
 
   unpackPhase = "dpkg-deb -x $src .";
 
-  installPhase = ''
-    mkdir -p $out
-    cp -R opt $out
-
-    mv ./usr/share $out/share
-    mv $out/opt/Signal $out/libexec
-    rmdir $out/opt
+  dontBuild = true;
+  dontConfigure = true;
+  dontPatchELF = true;
 
-    chmod -R g-w $out
+  installPhase = ''
+    mkdir -p $out/lib
 
-    # Patch signal
-    patchelf --set-interpreter "$(cat $NIX_CC/nix-support/dynamic-linker)" \
-             --set-rpath ${rpath}:$out/libexec $out/libexec/signal-desktop
-    wrapProgram $out/libexec/signal-desktop \
-      --prefix XDG_DATA_DIRS : "${gtk3}/share/gsettings-schemas/${gtk3.name}/" \
-      --prefix LD_LIBRARY_PATH : "${stdenv.cc.cc.lib}/lib" \
-      ${customLanguageWrapperArgs} \
-      "''${gappsWrapperArgs[@]}"
+    mv usr/share $out/share
+    mv opt/Signal $out/lib
 
     # Symlink to bin
     mkdir -p $out/bin
-    ln -s $out/libexec/signal-desktop $out/bin/signal-desktop
+    ln -s $out/lib/Signal/signal-desktop $out/bin/signal-desktop
+  '';
+
+  preFixup = ''
+    gappsWrapperArgs+=(
+      --prefix LD_LIBRARY_PATH : "${stdenv.lib.makeLibraryPath [ stdenv.cc.cc ] }"
+      ${customLanguageWrapperArgs}
+    )
 
     # Fix the desktop link
     substituteInPlace $out/share/applications/signal-desktop.desktop \