lttng-tools: 2.14.1 -> 2.15.1

https://github.com/lttng/lttng-tools/releases/tag/v2.15.1

Align with lttng-ust 2.15 and provide Python for the 2.15 test source generator.

Assisted-by: pi coding agent / Mika (OpenAI gpt-5.6-sol)

pkgs/by-name/lt/lttng-tools/package.nix

@@ -3,6 +3,7 @@
   stdenv,
   fetchurl,
   pkg-config,
+  python3,
   babeltrace2,
   popt,
   libuuid,
@@ -14,14 +15,21 @@
 
 stdenv.mkDerivation rec {
   pname = "lttng-tools";
-  version = "2.14.1";
+  version = "2.15.1";
 
   src = fetchurl {
     url = "https://lttng.org/files/lttng-tools/${pname}-${version}.tar.bz2";
-    sha256 = "sha256-DmjrJ5I2IcS8Enz85AQi0oz35HP+32IprmwyulxbfG0=";
+    sha256 = "sha256-i21Lp64sA299r7tOKXF2d0EQePmp2WGy3HwboWJz6ek=";
   };
 
-  nativeBuildInputs = [ pkg-config ];
+  nativeBuildInputs = [
+    pkg-config
+    python3
+  ];
+
+  # Used by the test source generator during the build.
+  makeFlags = [ "PYTHON=${lib.getExe python3}" ];
+
   buildInputs = [
     babeltrace2
     popt