riscv64: enable test summary printing

Author: xtexx

lib/compiler/test_runner.zig

@@ -292,6 +292,7 @@ pub fn mainSimple() anyerror!void {
     };
     // is the backend capable of using std.fmt.format to print a summary at the end?
     const print_summary = switch (builtin.zig_backend) {
+        .stage2_riscv64 => true,
         else => false,
     };