Merge pull request #2394 from verilog-to-routing/add_tbb_gaurd

Issue#2393 (add guards for tbb compilation)

Author: vaughnbetz

vpr/src/base/vpr_api.cpp

@@ -366,9 +366,12 @@ bool vpr_flow(t_vpr_setup& vpr_setup, t_arch& arch) {
         return true;
     }
 
+#ifdef VPR_USE_TBB
+
     /* Set this here, because tbb::global_control doesn't control anything once it's out of scope
      * (contrary to the name). */
     tbb::global_control c(tbb::global_control::max_allowed_parallelism, vpr_setup.num_workers);
+#endif
 
     { //Pack
         bool pack_success = vpr_pack_flow(vpr_setup, arch);