During compilation using an Ant script, if in one compiler group there are
multiple targets which have common dependencies, currently these common deps
will be run once for each using target. They should be shared, e.g. by making a
dummy target in the project listing all of the requested targets as dependencies
and running that instead.

Note that this would not affect the linear and unshared nature of targets which
are listed by the user in a row in AntCompilerType or AntExecutor; in the former
case, multiple levels of compilation are created (not the same group), and in
the latter the executor explicitly runs each in sequence anyway, which is
correct.