Main runs 40935337099, 40938407252 and 40941240624 (dd247e3) took at most
7m24s, 7m31s and 7m32s (Windows), so the limit is ceil(1.5 x 7m32s) + 3 =
15 min, down from 27. The tooling test recomputes the limit from the
measurements written above jobs:.