give a catch() a variable. gcc 8 is picky:

atf-check.cpp:221:23: error: catching polymorphic type 'class std::runtime_error' by value [-Werror=catch-value=]

external/bsd/atf/dist/atf-sh/atf-check.cpp

@@ -218,7 +218,7 @@ parse_signal(const std::string& str)
     if (signo == INT_MIN) {
         try {
             return atf::text::to_type< int >(str);
-        } catch (std::runtime_error) {
+        } catch (std::runtime_error &e) {
             throw atf::application::usage_error("Invalid signal name or number "
                 "in -s option");
         }