utf8: workaround gcc8's lack of char8_t

test/utf8.cpp

@@ -17,7 +17,13 @@ simple_valid (cruft::TAP::logger &tap)
         { "",        0, "empty string" },
         { "a",       1, "single ANSI character" },
         { "abc",     3, "multiple ANSI characters" },
+
+        // GCC#8 Disable u8 literals for compilers that support char8_t so
+        // that GCC's lack of support doesn't require a drastic and overly
+        // complicated workaround. Remove this condition when GCC9 is released.
+        #ifndef __cpp_char8_t
         { u8"κόσμε", 5, "greek kosme" },
+        #endif
     };
 
     static constexpr char fmt[] = "valid length, %s";