Blackbox all whiteboxes after synthesis

This prevents issues like processes in whiteboxes triggering an error in
the JSON backend.

Signed-off-by: gatecat <gatecat@ds0.me>

techlibs/intel/synth_intel.cc

@@ -233,6 +233,7 @@ struct SynthIntelPass : public ScriptPass {
 			run("hierarchy -check");
 			run("stat");
 			run("check -noinit");
+			run("blackbox =A:whitebox");
 		}
 
 		if (check_label("vqm")) {