[ci] improve formatting of build errors (#6811)
[ci] improve formatting of build errors (#6811)

Before this change we got an array of strings rather than
several lines
danking/hail,danking/hail,hail-is/hail,cseed/hail,cseed/hail,danking/hail,cseed/hail,cseed/hail,danking/hail,hail-is/hail,danking/hail,cseed/hail,hail-is/hail,hail-is/hail,cseed/hail,danking/hail,hail-is/hail,hail-is/hail,hail-is/hail,danking/hail,hail-is/hail,cseed/hail,danking/hail,cseed/hail