ziptool: fix unknown long options.

Previously an unknown long option would cause a crash as we ran off the
end of the array.

Test: `ziptool unzip --unknown`
Change-Id: I7a7b6ac4a0fa157c111f936e837c20143cef9e28

libziparchive/unzip.cpp

@@ -448,6 +448,7 @@ int main(int argc, char* argv[]) {
 
   static const struct option opts[] = {
       {"help", no_argument, 0, 'h'},
+      {},
   };
 
   if (role == kUnzip) {