[CMake] Mysterious build error that seems to have been slipstreamed into CMake 2.6

[kent williams]

We have an application based on the Slicer3 build. The Slicer3 build
downloads and builds CMake. We currently grab CMake with this command

cvs -q -d :pserver:anonymous at www.cmake.org:/cvsroot/CMake checkout -r
CMake-2-6 CMake

If I understand that correctly we're asking for the release tag of
2.6.  But up until today CMake built without problems and now I'm
getting this build error:

Linking CXX executable ../bin/cpack
/usr/bin/ld: Undefined symbols:
cmCPackComponent::GetInstalledSizeInKbytes(char const*) const
collect2: ld returned 1 exit status
make[2]: *** [bin/cpack] Error 1
make[1]: *** [Source/CMakeFiles/cpack.dir/all] Error 2
make: *** [all] Error 2

Are there changes being 'slipstreamed' into 2.6?