function safeTrimTrailingSeparator(p) {
    // Short-circuit if empty
    if (!p) {
        return '';
    }
    // Normalize separators
    p = normalizeSeparators(p);
    // No trailing slash
    if (!p.endsWith(path.sep)) {
        return p;
    }
    // Check '/' on Linux/macOS and '\' on Windows
    if (p === path.sep) {
        return p;
    }
    // On Windows check if drive root. E.g. C:\
    if (IS_WINDOWS && /^[A-Z]:\\$/i.test(p)) {
        return p;
    }
    // Otherwise trim trailing slash
    return p.substr(0, p.length - 1);
}
Normalizes the path separators and trims the trailing separator (when safe).
For example, `/foo/ => /foo` but `/ => /`