refactor: remove js2asar.py and port logic to JS in more readable / GN-style way (#16718)

* refactor: remove js2asar.py and port logic to JS in more readable / GN-style way

* refactor: further clean up ASAR impl, add new node_action GN template

script/gn-asar.js

@@ -0,0 +1,61 @@
+const asar = require('asar')
+const assert = require('assert')
+const fs = require('fs-extra')
+const os = require('os')
+const path = require('path')
+
+const getArgGroup = (name) => {
+  const group = []
+  let inGroup = false
+  for (const arg of process.argv) {
+    // At the next flag we stop being in the current group
+    if (arg.startsWith('--')) inGroup = false
+    // Push all args in the group
+    if (inGroup) group.push(arg)
+    // If we find the start flag, start pushing
+    if (arg === `--${name}`) inGroup = true
+  }
+
+  return group
+}
+
+const base = getArgGroup('base')
+const files = getArgGroup('files')
+const out = getArgGroup('out')
+
+assert(base.length === 1, 'should have a single base dir')
+assert(files.length >= 1, 'should have at least one input file')
+assert(out.length === 1, 'should have a single out path')
+
+// Ensure all files are inside the base dir
+for (const file of files) {
+  if (!file.startsWith(base[0])) {
+    console.error(`Expected all files to be inside the base dir but "${file}" was not in "${base[0]}"`)
+    process.exit(1)
+  }
+}
+
+const tmpPath = fs.mkdtempSync(path.resolve(os.tmpdir(), 'electron-gn-asar-'))
+
+try {
+  // Copy all files to a tmp dir to avoid including scrap files in the ASAR
+  for (const file of files) {
+    const newLocation = path.resolve(tmpPath, path.relative(base[0], file))
+    fs.mkdirsSync(path.dirname(newLocation))
+    fs.writeFileSync(newLocation, fs.readFileSync(file))
+  }
+} catch (err) {
+  console.error('Unexpected error while generating ASAR', err)
+  fs.removeSync(tmpPath)
+  process.exit(1)
+}
+
+// Create the ASAR archive
+asar.createPackageWithOptions(tmpPath, out[0], {}, (err) => {
+  fs.removeSync(tmpPath)
+
+  if (err) {
+    console.error('Unexpected error while generating ASAR', err)
+    process.exit(1)
+  }
+})