[boost] Boost.Build -q fix for 1.45

On IRC, Philipp Reh reported that 1.45 beta will fail if Boost.Build is invoked with -q, and any configuration test fails. The reason is that while Steven fixed this on trunk some time ago, I failed to merge to release branch. Since this bug means that Boost will outright not build in some cases, and since the fix is not really new, I think it should be checked in to release branch even at this point. The proposed diff is this: http://codepad.org/eoeawRoG Any objections before I go ahead? - Volodya