NativeScript can only run in Xcode version 6.0 or greater error is shown on every iOS command

[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: 5.2.3
• Cross-platform modules: Not applicable
• Android Runtime: Not applicable
• iOS Runtime: Not applicable
• Plugin(s): Not applicable

Describe the bug
Whenever I try to execute tns run ios, tns prepare ios, tns build ios, tns debug ios, etc. (i.e. every iOS related command), I receive an error: NativeScript can only run in Xcode version 6.0 or greater. However, my Xcode version is 10.1 (output of xcodebuild -version is:

Xcode 10.1
Build version 10B61

To Reproduce
The issue happens when the head command is overwritten by some other executable with head name. This happens in some cases related to Python, Go or XAMPP installations. The easiest way to reproduce the same behavior is to follow the steps below:

1. tns create myApp
2. cd myApp
3. echo "" > head (This will create file called head in your project directory.
4. chmod +x head (This will make the currently created head file executable.
5. Execute any iOS related command in the following manner:

PATH=`pwd`:$PATH tns prepare ios

This will set the PATH variable to contain the current working directory in the first place of your PATH, this way the head file we've just created will be used instead of the original head. NOTE: This command will set the PATH only for current command, so no need to worry about messing your machine.

Expected behavior
CLI should allow me to execute iOS related commands.

Related to: #3189 (comment)