add logging to integer/linear_programming; keep absl log symbols in libortools, enable GLPK in bazel

examples/cpp/linear_programming.cc

@@ -122,6 +122,7 @@ void RunAllExamples() {
 
 int main(int argc, char** argv) {
   InitGoogle(argv[0], &argc, &argv, true);
+  absl::SetFlag(&FLAGS_stderrthreshold, 0);
   operations_research::RunAllExamples();
   return EXIT_SUCCESS;
 }