This used to be a polyfill for require('child_process').spawnSync but now all actively maintained node versions already support spawnSync, so this is just a stub that re-exports spawnSync.
You should remove this library from your dependencies and just do:
var spawnSync = require('child_process').spawnSync;
var result = spawnSync('node',
['filename.js'],
{input: 'write this to stdin'});
if (result.status !== 0) {
process.stderr.write(result.stderr);
process.exit(result.status);
} else {
process.stdout.write(result.stdout);
process.stderr.write(result.stderr);
}MIT