shell check OS

gistfile1.txt

initOS() {
    OS=$(uname | tr '[:upper:]' '[:lower:]')
    if [ -n "$DEP_OS" ]; then
        echo "Using DEP_OS"
        OS="$DEP_OS"
    fi
    case "$OS" in
        darwin) OS='darwin';;
        linux) OS='linux';;
        freebsd) OS='freebsd';;
        mingw*) OS='windows';;
        msys*) OS='windows';;
        *) echo "OS ${OS} is not supported by this installation script"; exit 1;;
    esac
    echo "OS = $OS"
}