It should be possible for example to do this:
"$<AND:${FOO},$<BOOL:${TGT}>,$<BOOL:$<TARGET_PROPERTY:${TGT},PROP>"
such that it works simliarly to the C code:
if (foo && tgt && tgt->prop())
{
}
The example of generator expression code is a little bit contrived as
it could be written other ways with the same functionality. Nevertheless,
as these cases already work and are intentional, test for them.
4bacff7a4c