tauri fails to find Rez when Xcode (the app, not the command line tools) is not installed.

[caass]

Describe the bug
When Xcode Command Line Tools are installed, Rez is located at /Library/Developer/CommandLineTools/usr/bin/Rez. Tauri looks in /Applications/Xcode.app/Contents/Developer/Tools/Rez, which doesn't exist if the Xcode app is not installed.

To Reproduce
Steps to reproduce the behavior:

1. Uninstall Xcode if it is installed on your system
2. Run xcode-select --install to install Xcode Command Line Tools
3. Run tauri build --verbose
4. Tauri will display the following error when attempting to find Rez:

adding EULA resources
Failed to find Rez at "/Applications/Xcode.app/Contents/Developer/Tools/Rez"!

Usage: dmg-license.py <dmgFile> <licenseFile> [OPTIONS]
  This program adds a software license agreement to a DMG file.
  It requires Xcode and either a plain ascii text <licenseFile>
  or a <licenseFile.rtf> with the RTF contents.

  See --help for more details.

error: Shell Scripting Error:`error running bundle_dmg.sh`

Expected behavior
Tauri checks if Xcode is installed, and if not, looks for the Command Line Tools. If neither are found a human-readable error is thrown telling the user to run xcode-select --install

Screenshots
If applicable, add screenshots to help explain your problem.

Platform and Versions (please complete the following information):

Operating System - Darwin(19.6.0) - darwin/x64

Node.js environment
  Node.js - 14.8.0
  tauri.js - 0.12.0

Rust environment
  rustc - 1.45.2
  cargo - 1.45.1
  tauri-bundler - 0.9.2

Global packages
  NPM - 6.14.7
  yarn - 1.22.4

Additional context
As a workaround I'm just installing Xcode, although it would be nice if this was patched so I could save some space on my hard drive 😅

Thanks so much for your tireless work on this project! It's been a surprisingly smooth experience getting up and running with Tauri, even with limited Rust knowledge ❤️