Function proxy_content 

pub fn proxy_content(
    vendor_dir: &Path,
    link: &Path,
    bin: &Path,
) -> Result<String>

Generates the content of the proxy link (vendor/bin/) to the binary bin (absolute, inside vendor/ or outside it with composer/installers), reading the target’s header. Relative paths are those of BinaryInstaller::installUnixyProxyBinaries (findShortestPath from the proxy file).