rPackages.rextendr: fix missing cargo (#430012)

      LIBAPPARMOR_HOME = pkgs.libapparmor;

    });

    # Append cargo path to path variable

    # This will provide cargo in case it's not set by the user

    rextendr = old.rextendr.overrideAttrs (attrs: {

      postPatch = ''

        substituteInPlace R/zzz.R --replace-fail \

          ".onLoad <- function(...) {" \

          '.onLoad <- function(...) {

           Sys.setenv(PATH = paste0(Sys.getenv("PATH"), ":${lib.getBin pkgs.cargo}/bin"))'

      '';

    });

    RMySQL = old.RMySQL.overrideAttrs (attrs: {

      MYSQL_DIR = "${pkgs.libmysqlclient}";

      PKGCONFIG_CFLAGS = "-I${pkgs.libmysqlclient.dev}/include/mysql";