Commit 438a7e2f (Fix utility dependencies for static libraries in VS
generators, 2007-04-04) implemented utility-only dependencies between
linkable targets by introducing an intermediate non-linkable target.
We convert a dependency of the form

  foo -> bar

to the form

  foo -> bar_UTILITY -> bar

to prevent foo from including bar on its link line.  Previously we added
the extra "_UTILITY" targets explicitly among the project targets before
dependency analysis was performed.  Now we generate them separately at
the last moment so that cmGlobalGenerator need not be aware of them.