'target' : not all dependents available; target not built
A dependent of the given target either did not exist or was out-of-date, and a command for updating the dependent returned a nonzero exit code. The /K option told NMAKE to continue processing unrelated parts of the build and to issue an exit code 1 when the NMAKE session is finished.
This warning is preceded by warning U4010 for each dependent that failed to be created or updated.