appveyor: don't double build
appveyor: don't double build

The integration tests build the multicall executable a second time, so
we disable the original build and only run the tests.

wimh/coreutils,keunwoo/coreutils,keunwoo/coreutils,uutils/coreutils,uutils/coreutils,ebfe/coreutils,Arcterus/coreutils,kwantam/coreutils,uutils/coreutils,kevgeniy/coreutils,tempbottle/coreutils,wimh/coreutils,tempbottle/coreutils,jbcrail/coreutils,Heather/coreutils,Arcterus/coreutils,jbcrail/coreutils,ebfe/coreutils,kevgeniy/coreutils,Heather/coreutils,kwantam/coreutils