bootstrap: Always use npm install (not npm ci)

This change only affects the CI environment.

Allows better re-use of existing installed packages
(such as those restored from a cache).

`npm ci` and `apm ci` forced a fresh reinstall of packages,
including rebuilding all native code.

Rebuilding native code accounts for the majority of install time.

By not rebuilding native code unless totally necessary,
`npm install` and `apm install` can save a lot of time versus
`npm ci` and `apm ci`.

Author: DeeDeeG

script/lib/install-script-dependencies.js

@@ -9,8 +9,8 @@ process.env.ELECTRON_CUSTOM_VERSION = CONFIG.appMetadata.electronVersion;
 module.exports = function(ci) {
   console.log('Installing script dependencies');
   childProcess.execFileSync(
-    CONFIG.getNpmBinPath(ci),
-    ['--loglevel=error', ci ? 'ci' : 'install'],
+    CONFIG.getNpmBinPath(),
+    ['--loglevel=error', 'install'],
     { env: process.env, cwd: CONFIG.scriptRootPath }
   );
 };

script/lib/run-apm-install.js

@@ -11,7 +11,7 @@ module.exports = function(packagePath, ci, stdioOptions) {
   // Set our target (Electron) version so that node-pre-gyp can download the
   // proper binaries.
   installEnv.npm_config_target = CONFIG.appMetadata.electronVersion;
-  childProcess.execFileSync(CONFIG.getApmBinPath(), [ci ? 'ci' : 'install'], {
+  childProcess.execFileSync(CONFIG.getApmBinPath(), ['install'], {
     env: installEnv,
     cwd: packagePath,
     stdio: stdioOptions || 'inherit'