fix: make xcode_emulation handle xcodebuild not in the PATH

[aduh95]

As titled, when trying to run the script in an environment that doesn't have any xcodebuild in the path, it crashes with a FileNotFoundError instead of falling back to the XCode Command Line Tools.

[cclauss]

I liked the targeted FileNotFoundError over the more general IOError because it describes the problem we are trying to fix. Other IOErrors are unexpected and should probably be raised, but either solution should work.

[aduh95]

I liked the targeted FileNotFoundError over the more general IOError because it describes the problem we are trying to fix. Other IOErrors are unexpected and should probably be raised, but either solution should work.

I don't have a strong opinion, I would note that given all those paths have a fallback, it's probably fine to ignore those OSErrors as long as any fallback ends up working – if not, it will reach raise GypError("No Xcode or CLT version detected!"), at which point the user must address the underlining issue.

For reference, here's the list of OSErrors according to Python doc:

      ├── OSError
      │    ├── BlockingIOError
      │    ├── ChildProcessError
      │    ├── ConnectionError
      │    │    ├── BrokenPipeError
      │    │    ├── ConnectionAbortedError
      │    │    ├── ConnectionRefusedError
      │    │    └── ConnectionResetError
      │    ├── FileExistsError
      │    ├── FileNotFoundError
      │    ├── InterruptedError
      │    ├── IsADirectoryError
      │    ├── NotADirectoryError
      │    ├── PermissionError
      │    ├── ProcessLookupError
      │    └── TimeoutError

[cclauss]

OPTIONAL: rm xcodebuild tests would be a nice addition.