mtxclient: fix build on aarch64-linux

pkgs/development/libraries/mtxclient/default.nix

@@ -53,6 +53,9 @@ stdenv.mkDerivation rec {
     spdlog
   ];
 
+  # https://github.com/NixOS/nixpkgs/issues/201254
+  NIX_LDFLAGS = lib.optionalString (stdenv.isLinux && stdenv.isAarch64 && stdenv.cc.isGNU) "-lgcc";
+
   meta = with lib; {
     description = "Client API library for the Matrix protocol.";
     homepage = "https://github.com/Nheko-Reborn/mtxclient";

pkgs/top-level/all-packages.nix

@@ -22021,7 +22021,10 @@ with pkgs;
 
   mtpfs = callPackage ../tools/filesystems/mtpfs { };
 
-  mtxclient = callPackage ../development/libraries/mtxclient { };
+  mtxclient = callPackage ../development/libraries/mtxclient {
+    # https://github.com/NixOS/nixpkgs/issues/201254
+    stdenv = if stdenv.isLinux && stdenv.isAarch64 && stdenv.cc.isGNU then gcc11Stdenv else stdenv;
+  };
 
   mu = callPackage ../tools/networking/mu {
     texinfo = texinfo4;