As they attempt to enter the building spray them all with a 1:5 solution of cadaverine. Follow that with a couple of fire hoses to hose down the steps of the building to wash away the results of their retching, along with them.
None of it is permanent as such although like skunk spray it takes time and a lot of effort to rid yourself of it. On your clothes, you will need to burn them or bury them.
Depending on how you wash off cadaverine or putrescine, you can get away with just smelling like really foul urine for a few weeks. Amines can be powerful odiferous compounds.
Permanent skunk spray? Yeah, the skunks do. Every now and then I trap one by accident and the stink lasts until a buzzard hauls off the carcass. And that bit of wisdom could be related to hauling off these dirtbagz.