How much effort goes into maintaining a build system?

Question

In StackExchange Podcast #09 it is remarked:

Another study recently looked at how much effort goes into maintaining the build system: 5 to 30% of all development effort is spent on maintaining the build system. With the variations being huge even when working on similar projects.

What is the name of the study referenced, and where can it be found? The audio of the podcast contains no further details.

Additionally, does anyone have any links to other studies covering the same topic.