[Examples] Make sure that clangd-contexts build script has sufficient permissions

### Feature Description:
I just noticed that on my local machine in the electron variant (packaged or built from sources) the generated `build.sh` script from the `clangd-contexts` example failed with a `permission denied` for me. It was an easy fix using `chmod +x ./build.sh`, but we should either document this or even better, make sure that the file has the correct permissions after we copied it.