lomiri.libusermetrics: Add custom patch for launching systemd service

The UserMetrics service expects AppArmor to be available, and its database access breaks when that's not the case.
Details: https://gitlab.com/ubports/development/core/libusermetrics/-/issues/8

We need to set an envvar for it to work AppArmor-less, but that requires system config knowledge.
Solve this by telling the D-Bus service to look for & launch a systemd service, which we will later create in the Lomiri module.

pkgs/desktops/lomiri/development/libusermetrics/2002-Launch-module-created-systemd-service.patch

@@ -0,0 +1,21 @@
+From cf8ba54d22f5ac839004c0d984fb402bde82b527 Mon Sep 17 00:00:00 2001
+From: OPNA2608 <opna2608@protonmail.com>
+Date: Mon, 8 Apr 2024 15:22:55 +0200
+Subject: [PATCH] Launch module-created systemd service
+
+---
+ data/com.lomiri.UserMetrics.service.in | 1 +
+ 1 file changed, 1 insertion(+)
+
+diff --git a/data/com.lomiri.UserMetrics.service.in b/data/com.lomiri.UserMetrics.service.in
+index c2e6ae1..212e24f 100644
+--- a/data/com.lomiri.UserMetrics.service.in
++++ b/data/com.lomiri.UserMetrics.service.in
+@@ -3,3 +3,4 @@ Name=com.lomiri.UserMetrics
+ Exec=@CMAKE_INSTALL_FULL_LIBEXECDIR@/libusermetrics/usermetricsservice
+ User=usermetrics
+ StandardOutput=syslog
++SystemdService=dbus-com.lomiri.UserMetrics.service
+-- 
+2.42.0
+

pkgs/desktops/lomiri/development/libusermetrics/default.nix

@@ -43,6 +43,10 @@ stdenv.mkDerivation (finalAttrs: {
   patches = [
     # Not submitted yet, waiting for decision on how CMake testing should be handled
     ./2001-Remove-custom-check-target.patch
+
+    # Due to https://gitlab.com/ubports/development/core/libusermetrics/-/issues/8, we require knowledge about AppArmor availability at launch time
+    # Custom patch to launch a module-defined service that can handle this
+    ./2002-Launch-module-created-systemd-service.patch
   ];
 
   postPatch = ''
@@ -91,6 +95,7 @@ stdenv.mkDerivation (finalAttrs: {
   cmakeFlags = [
     (lib.cmakeBool "GSETTINGS_LOCALINSTALL" true)
     (lib.cmakeBool "GSETTINGS_COMPILE" true)
+    (lib.cmakeBool "ENABLE_CLICK" true)
     (lib.cmakeBool "ENABLE_TESTS" finalAttrs.finalPackage.doCheck)
     (lib.cmakeFeature "CMAKE_CTEST_ARGUMENTS" (lib.concatStringsSep ";" [
       # Exclude tests