The specific error is:
build.bat: *ERROR* The target executable does not exist:
build.bat: Please make sure you have checked out the 'tools' module
build.bat: and make sure it is up to date.
I'm trying to recall what I did because I have 2.4CR1 source on my PC, and it looks like I built it. But I think what I did is download both the binary and the source. I did build the source by running build without any targets. But for the *-ds.xml file, I think I got that from the binary download.
Found the datasource target. You have to be in the core directory to run "build datasource". Surprisingly enough, that is what the instructions in the reference guide say.