test: make debugging of inspector-port-zero easier

If the process was killed, then the exit code will be null, in which
case knowing the signal is really helpful.

PR-URL: #16685
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Eugene Ostroukhov <eostroukhov@google.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

test/sequential/test-inspector-port-zero.js

@@ -34,7 +34,10 @@ function test(arg, port = '') {
     };
     proc.stdout.on('close', mustCall(() => onclose()));
     proc.stderr.on('close', mustCall(() => onclose()));
-    proc.on('exit', mustCall((exitCode) => assert.strictEqual(exitCode, 0)));
+    proc.on('exit', mustCall((exitCode, signal) => assert.strictEqual(
+      exitCode,
+      0,
+      `exitCode: ${exitCode}, signal: ${signal}`)));
   }
 }