CDash build ID not set (CTest, CMake)

I have a CDash configured to accept posts for automatic builds and tests. However, when any system attempts to post results to the CDash, the following error is produced. The result is that each result gets posted four times (presumably the original posting attempt plus the three retries).

Can anyone give me a hint as to what sets this mysterious build ID? I found some code that seems to produce a similar error, but still no lead on what might be happening.

Build::GetNumberOfErrors(): BuildId 开发者_如何转开发not set

Build::GetNumberOfWarnings(): BuildId not set

Submit failed, waiting 5 seconds...

Retry submission: Attempt 1 of 3

Server Response:

The buildid for CDash is computed based on the site name, the build name and the build stamp of the submission. You should have a Build.xml file in a Testing/20110311-* directory in your build tree. Open that up and see if any of those fields (near the top) is empty. If so, you need to set BUILDNAME and SITE with -D args when configuring with CMake. Or, set CTEST_BUILD_NAME and CTEST_SITE in your ctest -S script.

If that's not it, then this is a mystery. I've not seen this error occur before...