child_process: restore exec{File}Sync error props

In PR [1], a bunch of properties were removed from the error thrown by
execSync and execFileSync. It turns out that some of those were still
supposed to be there, as the documentation states that the error
contains the entire result from the spawnSync call.

[1] nodejs#13601

lib/child_process.js

@@ -574,8 +574,7 @@ function checkExecSyncError(ret, args, cmd) {
     err = new Error(msg);
   }
   if (err) {
-    err.status = ret.status < 0 ? errname(ret.status) : ret.status;
-    err.signal = ret.signal;
+    Object.assign(err, ret);
   }
   return err;
 }

test/sequential/test-child-process-execsync.js

@@ -23,7 +23,7 @@
 const common = require('../common');
 const assert = require('assert');
 
-const { execFileSync, execSync } = require('child_process');
+const { execFileSync, execSync, spawnSync } = require('child_process');
 
 const TIMER = 200;
 const SLEEP = 2000;
@@ -112,6 +112,8 @@ assert.strictEqual(ret, `${msg}\n`);
 // Verify the execFileSync() behavior when the child exits with a non-zero code.
 {
   const args = ['-e', 'process.exit(1)'];
+  const spawnSyncResult = spawnSync(process.execPath, args);
+  const spawnSyncKeys = Object.keys(spawnSyncResult);
 
   assert.throws(() => {
     execFileSync(process.execPath, args);
@@ -121,6 +123,11 @@ assert.strictEqual(ret, `${msg}\n`);
     assert(err instanceof Error);
     assert.strictEqual(err.message, msg);
     assert.strictEqual(err.status, 1);
+    assert.strictEqual(typeof err.pid, 'number');
+    spawnSyncKeys.forEach((key) => {
+      if (key === 'pid') return;
+      assert.deepStrictEqual(err[key], spawnSyncResult[key]);
+    });
     return true;
   });
 }