function isRooted(p) {
    p = normalizeSeparators(p);
    if (!p) {
        throw new Error('isRooted() parameter "p" cannot be empty');
    }
    if (exports.IS_WINDOWS) {
        return (p.startsWith('\\') || /^[A-Z]:/i.test(p) // e.g. \ or \hello or \\hello
        ); // e.g. C: or C:\hello
    }
    return p.startsWith('/');
}
On OSX/Linux, true if path starts with '/'. On Windows, true for paths like:
\, \hello, \\hello\share, C:, and C:\hello (and corresponding alternate separator cases).