Update macos-build-script.sh

Add OpenCV installation check to build script

- Add a new step to check if OpenCV is installed before proceeding.
- Avoid cryptic failures later in build if OpenCV is missing.
- Standardize logging format for install check steps.
- Detailed INFO and ERROR messages for clear visibility.
- Script is now more robust with explicit dependency checking.
- Fail fast if required libraries like OpenCV are not available.