[tfjs-node] Add new line when saving package.json through code

[kangyizhang]

Currently scripts/install.js add a field in package.json during installation and then remove it at the end of installation. But when saving the package.json file it removes the last line and cause unexpected change.

This PR add a newline at the end of package.json when saving it, and use writeFileSync.

---

This change is 

[caisq]

Reviewable status: 0 of 1 approvals obtained (waiting on @caisq and @kangyizhang)

---

tfjs-node/scripts/install.js, line 69 at r1 (raw file):

writeFileSync(

Why is it necessary to change writeFile() towriteFileSync() in this PR? If you want to change this, you should change the error callback function (the 3rd argument) as well, right?

[kangyizhang]

Reviewable status: complete! 1 of 1 approvals obtained (waiting on @caisq)

---

tfjs-node/scripts/install.js, line 69 at r1 (raw file):

Previously, caisq (Shanqing Cai) wrote…

writeFileSync(

Why is it necessary to change writeFile() towriteFileSync() in this PR? If you want to change this, you should change the error callback function (the 3rd argument) as well, right?

It's not necessary in this PR and you are right the callback argument should be removed. Now if writeFileSync failed it will throw an exception.

Using writeFileSync will make sure the new field is added in package.json before node-gyp binding read the package.json file.