Guatemala’s army detained a boat carrying a supply of abortion pills on Thursday and prevented it from picking up women seeking to end their pregnancies, saying the move was prohibited by the country’s constitution. The boat, operated by Dutch nonprofit Women on Waves, was in military custody with some of its seven crew members still aboard, after landing at a private pier at the Port of San Jose, 75 miles south of the capital, said Leticia Zenevich, a spokeswoman for the group.