International employment contract between a football club and a Brazilian player. Possibility of adjudicating a contractual employment termination via arbitration, given that there was no waiver of a labor right (which is non-waivable), but merely the application of a termination penalty. Validity of the stipulation establishing adjustment based on exchange rate variation, provided that payment is made in national currency, if effected in Brazil, absence of violation of Article 6 of Law 8.880/94: