test: avoid trying to call sysctl directly

sysctl is often installed in /usr/sbin, which is not conveniently
accessible to non-root. Secondly, the setting can just be read
directly from the standard location and does not need to be
parsed in any special fashion.

PR-URL: #46366
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Richard Lau <rlau@redhat.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

test/parallel/test-cluster-bind-privileged-port.js

@@ -24,11 +24,10 @@ const common = require('../common');
 const assert = require('assert');
 const cluster = require('cluster');
 const net = require('net');
-const { execSync } = require('child_process');
+const { readFileSync } = require('fs');
 
 if (common.isLinux) {
-  const sysctlOutput = execSync('sysctl net.ipv4.ip_unprivileged_port_start').toString();
-  const unprivilegedPortStart = parseInt(sysctlOutput.split(' ')[2], 10);
+  const unprivilegedPortStart = parseInt(readFileSync('/proc/sys/net/ipv4/ip_unprivileged_port_start'));
   if (unprivilegedPortStart <= 42) {
     common.skip('Port 42 is unprivileged');
   }