Add iOs platform never stops

**Description:**
When executing the command `ionic cordova platform add ios`, it stops on "Generating platform resources: 29 / 32 complete", sometimes "31/32" but never ends. If I abort the command, I then have errors when running my ionic app on iOs.

**Steps to Reproduce:**
Execute the command `ionic cordova platform add ios`

**Output:**
> cordova platform add ios --save
✔ Running command - done!
> ionic cordova resources ios --force
[DEBUG] resourceJsonStructure=3
[DEBUG] platformEngines=ios
[DEBUG] buildPlatforms=ios
[DEBUG] getProjectPlatforms completed - length=1
[DEBUG] imgResources=32
[DEBUG] createImgDestinationDirectories completed - length=2
[DEBUG] getSourceImages completed - 2
✔ Collecting resource configuration and source images - done!
✔ Filtering out image resources that do not need regeneration - done!
[DEBUG] uploadSourceImages completed - responses=[
{},
{}
]
✔ Uploading source images to prepare for transformations - done!
⠼ Generating platform resources: 28 / 32 complete

**My `ionic info`:**
cli packages: (/usr/local/lib/node_modules)

@ionic/cli-utils : 1.12.0
ionic (Ionic CLI) : 3.12.0

global packages:

cordova (Cordova CLI) : 7.0.1

local packages:

@ionic/app-scripts : 3.0.0
Cordova Platforms : ios 4.4.0
Ionic Framework : ionic-angular 3.7.1

System:

ios-deploy : 1.9.1
Node : v7.7.2
npm : 4.1.2
OS : macOS Sierra
Xcode : Xcode 8.2.1 Build version 8C1002

Misc:

backend : pro

Start by reproducing `ionic cordova platform add ios` with the versions and macOS/Xcode environment listed in the issue, focusing on the resource-generation step that stalls near completion. Trace the CLI entry point for `ionic cordova resources ios --force` and identify why generation does not finish. Done means the command completes and the Ionic app can run on iOS without the errors caused by aborting it.

Written by the indexing model from the issue text.