Xcode, Command Line Tools, GCC, and HomeBrew
Judging from the following command line output:

xcode-select: error: command line tools are already installed, use "Software Update" to install updates.


it appears that you only have Xcode's command line tools installed. They are a requirement for running homebrew.

To build iOS apps you will have to download the full xcode package with the IDE and all the necessary tools. You can get Xcode from the AppStore: Link