[Vitis] update args for v++ with optimize and report

src/finn/transformation/fpgadataflow/vitis_build.py

@@ -238,7 +238,7 @@ class VitisLink(Transformation):
             f.write("cd {}\n".format(link_dir))
             f.write(
                 "v++ -t hw --platform %s --link %s"
-                " --kernel_frequency %d --config config.txt\n"
+                " --kernel_frequency %d --config config.txt --optimize 2 --save-temps -R2\n"
                 % (self.platform, " ".join(object_files), self.f_mhz)
             )
             f.write("cd {}\n".format(working_dir))