What is the ruling on an architect working on the construction of a stock exchange if that is unavoidable, otherwise he would be forced to leave the company?

The stock market is permissible in principle. Designing a building for it or participating in its construction does not directly involve the unlawful (haram) nor does it constitute intentional assistance to it. Assistance in sin and transgression is divided into four categories: direct and intentional, direct and unintentional, intentional and indirect, and neither direct nor intentional. The Assembly of Muslim Jurists of America has permitted the fourth category and prohibited the first three.