ueransim: backport gcc-15 fix

Without the change the build fails on `master` as
https://hydra.nixos.org/build/320137255:

    /build/source/src/ext/yaml-cpp/emitterutils.cpp:221:11: error: 'uint16_t' was not declared in this scope
      221 | std::pair<uint16_t, uint16_t> EncodeUTF16SurrogatePair(int codePoint) {
          |           ^~~~~~~~

pkgs/by-name/ue/ueransim/package.nix

@@ -4,6 +4,7 @@
   cmake,
   pkg-config,
   fetchFromGitHub,
+  fetchpatch,
   lksctp-tools,
   iproute2,
   unstableGitUpdater,
@@ -20,6 +21,16 @@ stdenv.mkDerivation (finalAttrs: {
     hash = "sha256-8OxJzEcpFT6e/nQw1VK9kBdw9ulXedCpUEaBxIAN9cA=";
   };
 
+  patches = [
+    # Fix gcc-15 build failure:
+    #   https://github.com/aligungr/UERANSIM/pull/777
+    (fetchpatch {
+      name = "gcc-15.patch";
+      url = "https://github.com/aligungr/UERANSIM/commit/8ffce535a11b63f688552c5c81f7d3ac793f47de.patch";
+      hash = "sha256-w2T7PTR/ELNf9sre/GoHqZQb9A8k54cTKoce/RZ7XCU=";
+    })
+  ];
+
   nativeBuildInputs = [
     cmake
     pkg-config