timeloop: fix gcc-13 build failure

Without the change build fails on `master` as
https://hydra.nixos.org/build/248973743:

    include/compound-config/compound-config.hpp:149:8: error: ‘uint64_t’ in namespace ‘std’ does not name a type; did you mean ‘wint_t’?
      149 |   std::uint64_t parseElementSize(std::string name);
          |        ^~~~~~~~
          |        wint_t

pkgs/applications/science/computer-architecture/timeloop/default.nix

@@ -46,6 +46,10 @@ stdenv.mkDerivation rec {
   env.NIX_CFLAGS_COMPILE = lib.optionalString stdenv.isDarwin "-fno-lto";
 
   postPatch = ''
+    # Fix gcc-13 build failure due to missing includes:
+    sed -e '1i #include <cstdint>' -i \
+      include/compound-config/compound-config.hpp
+
     # use nix ar/ranlib
     substituteInPlace ./SConstruct \
       --replace "env.Replace(AR = \"gcc-ar\")" "" \