dmd: pull in missing libgcc.so dependency

Without the change autopatchelf fails to find the dependency as:

    searching for dependencies of ...-dmd-bootstrap-2.090.1/bin/dmd
        libgcc_s.so.1 -> not found!
    auto-patchelf: 6 dependencies could not be satisfied

Full build log: https://hydra.nixos.org/log/plma45m19p0cm1i04c4qzmfi54n38ydk-dmd-bootstrap-2.090.1.drv

pkgs/development/compilers/dmd/binary.nix

@@ -28,6 +28,7 @@ in stdenv.mkDerivation {
     tzdata
   ] ++ lib.optionals hostPlatform.isLinux [
     glibc
+    stdenv.cc.cc.libgcc
   ];
 
   installPhase = ''