Try fix

assembly/nix/linux-arm64-tonlib.nix

@@ -2,7 +2,6 @@
 {
   pkgs ? import <nixpkgs> { inherit system; }
 , lib ? pkgs.lib
-, stdenv ? pkgs.stdenv
 , system ? builtins.currentSystem
 , src ? ./.
 }:
@@ -46,12 +45,10 @@ pkgs.llvmPackages_16.stdenv.mkDerivation {
     "-DMHD_FOUND=1"
     "-DMHD_INCLUDE_DIR=${microhttpdmy}/usr/local/include"
     "-DMHD_LIBRARY=${microhttpdmy}/usr/local/lib/libmicrohttpd.a"
-    "-DCMAKE_CXX_FLAGS=-w"
     "-DCMAKE_C_FLAGS=-w"
     "-DCMAKE_CXX_STANDARD=20"
+    "-DCMAKE_CXX_STANDARD_REQUIRED=ON"
     "-DCMAKE_CXX_FLAGS=-Wno-deprecated-declarations -Wno-unused-but-set-variable"
-    "-DCMAKE_C_COMPILER=clang"
-    "-DCMAKE_CXX_COMPILER=clang++"
   ];
 
   LDFLAGS = [

assembly/nix/linux-x86-64-tonlib.nix

@@ -20,7 +20,7 @@ let
       libc = glibc227;
       bintools = pkgs.binutils.override { libc = glibc227; };
     };
-  in (pkgs.overrideCC pkgs.stdenv cc);
+  in (pkgs.overrideCC pkgs.gcc12Stdenv cc);
   staticLibs = import ./static-libs.nix { inherit pkgs; };
 in
 stdenv227.mkDerivation {

flake.nix

@@ -64,20 +64,6 @@
       (eachSystem (with system; [ x86_64-linux aarch64-linux ]) (system:
         let
           host = hostPkgs system;
-
-          nixos1909 = (import (builtins.fetchTarball {
-                      url = "https://channels.nixos.org/nixos-19.09/nixexprs.tar.xz";
-                      sha256 = "1vp1h2gkkrckp8dzkqnpcc6xx5lph5d2z46sg2cwzccpr8ay58zy";
-                    }) { inherit system; });
-                    glibc227 = nixos1909.glibc // { pname = "glibc"; };
-                    stdenv227 = let
-                      cc = host.wrapCCWith {
-                        cc = nixos1909.buildPackages.gcc-unwrapped;
-                        libc = glibc227;
-                        bintools = host.binutils.override { libc = glibc227; };
-                      };
-                    in (host.overrideCC host.stdenv cc);
-
           tonk = kind: ton {
             inherit host;
             inherit system;