test: print child stderr in test-http-chunk-problem

This helps with debugging test failures.

PR-URL: #27117
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Beth Griggs <Bethany.Griggs@uk.ibm.com>
Reviewed-By: Yongsheng Zhang <zyszys98@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>

Author: addaleax

test/parallel/test-http-chunk-problem.js

@@ -52,6 +52,9 @@ function executeRequest(cb) {
            `"${__filename}"`,
            'shasum' ].join(' '),
           (err, stdout, stderr) => {
+            if (stderr.trim() !== '') {
+              console.log(stderr);
+            }
             assert.ifError(err);
             assert.strictEqual(stdout.slice(0, 40),
                                '8c206a1a87599f532ce68675536f0b1546900d7a');