test: use common.js to check platform

PR-URL: #12629
Reviewed-By: Daniel Bevenius <[email protected]>
Reviewed-By: Anna Henningsen <[email protected]>
Reviewed-By: James M Snell <[email protected]>
Reviewed-By: Colin Ihrig <[email protected]>
Reviewed-By: Luigi Pinca <[email protected]>
Reviewed-By: Richard Lau <[email protected]>
Reviewed-By: Gibson Fahnestock <[email protected]>
Reviewed-By: Vse Mozhet Byt <[email protected]>

Author: krydos

test/parallel/test-fs-readfile-error.js

@@ -6,7 +6,7 @@ const path = require('path');
 
 // `fs.readFile('/')` does not fail on FreeBSD, because you can open and read
 // the directory there.
-if (process.platform === 'freebsd') {
+if (common.isFreeBSD) {
   common.skip('platform not supported.');
   return;
 }