tns devices --availableDevices prompts to install Xcode command line tools

[rosen-vladimirov]

Environment
Provide version numbers for the following components (information can be retrieved by running tns info in your project folder or by inspecting the package.json of the project):

• CLI: 5.1.1
• Cross-platform modules: Not Applicable
• Android Runtime: Not Applicable
• iOS Runtime: Not Applicable
• Plugin(s): Not Applicable

Describe the bug
In case Xcode and Xcode Command Line tools are not installed, calling tns run or tns devices --availableDevices leads to a UI prompt (from the OS) to install the missing components.

To Reproduce
On a macOS without Xcode execute tns devices --availableDevices

Expected behavior
The command should list the currently attached devices/available devices, but should not prompt me to install anything.