Previous code used default-build attribute to cause a number
of property sets be requested, and then used indirect
conditional requirements to filter out inappropriate ones,
using the <build>no feature. This worked but is messy, and resulted
in a pile of unclear messages about <build>no. This patch
introduces custom main target class that handles filtering,
so we don't ever try to build with undesired property sets.
[SVN r52319]
13a2d76893
