Do not assume that __float128 exists

The code in build_round_expr implicitly assumes that __float128 exists,
which is *not* the common case among 64-bit architectures since the
"long double" type is generally already 128-bit for them.

gcc/fortran/
	PR fortran/96983
	* trans-intrinsic.c (build_round_expr): Do not implicitly assume
	that __float128 is the 128-bit floating-point type.

gcc/fortran/trans-intrinsic.c

@@ -407,7 +407,7 @@ build_round_expr (tree arg, tree restype)
       if (kind < 0)
 	gfc_internal_error ("Could not find real kind with at least %d bits",
 			    resprec);
-      arg = fold_convert (gfc_float128_type_node, arg);
+      arg = fold_convert (gfc_get_real_type (kind), arg);
       fn = gfc_builtin_decl_for_float_kind (BUILT_IN_ROUND, kind);
     }
   else