In the TFS 2010 build summary, how do I show the link to the logs from the custom MSBuild task?

In my TFS 2010 build definition, I call MSBuild in my own my.targets MSBuild project. It does all the compilation, testing, etc. that I need. Its log file is listed, as well as the location to delete the log, and the log displays correctly in that location. However, I do not see it in the TFS Build Summary report. The View Log File link is grayed out. This seemed to work when the project I was building was a .sln file. What magical voodoo has baked deeply at the heart of MSBuild shared files so that this work is handled correctly, and how can I reproduce it?