Gowin. Ignore empty lines.

Including those containing nothing but spaces and tabs.

Fixes https://github.com/YosysHQ/apicula/issues/432

Signed-off-by: YRabbit <rabbit@yrabbit.cyou>

himbaechel/uarch/gowin/cst.cc

@@ -112,6 +112,11 @@ struct GowinCstReader
 
             while (!in.eof()) {
                 std::getline(in, line);
+                boost::trim_right(line);
+                if (line.empty()) {
+                    continue;
+                }
+
                 cst_type = ioloc;
                 if (!std::regex_match(line, match, iobre)) {
                     if (std::regex_match(line, match, portre)) {