fix regression in access to optopt object

commit b9410061e2ad6fe91bb3910c3adc7d4a315b7ce9 inadvertently omitted
optopt from the "dynamic list", causing it to be split into separate
objects that don't share their value if the main program contains a
copy relocation for it (for non-PIE executables that access it, and
some PIE ones, depending on arch and toolchain versions/options).

dynamic.list

@@ -28,6 +28,7 @@ __signgam;
 optarg;
 optind;
 opterr;
+optopt;
 optreset;
 __optreset;