fix regression in access to optopt object

commit b9410061e2 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;