What is the ruling on committing a sin that is not among the major sins in order to avoid committing two sins at the same time?

It is obligatory for a Muslim to repent from all sins. No one has an excuse for committing a sin unless they are legally compelled. What you have mentioned is not an excuse for committing this sin. It is obligatory to repent to Allah from this sin and from all other sins, and to adhere steadfastly to Allah's law through performing the obligatory acts and supererogatory acts, and by avoiding forbidden acts. One must beware of the consequences of sins, for complacency with minor sins leads to greater ones. Seek assistance in repentance through the companionship of the righteous, supplication, and constant remembrance of the Hereafter. And whoever strives for the sake of Allah, Allah will aid them in guidance.