[C++] Unconditonally checks --generate_all_phony_targets
[C++] Unconditonally checks --generate_all_phony_targets

This flag should work even with targets specified in a command
line.

colincross/kati,colincross/kati,google/kati,google/kati,shinh/kati,google/kati,google/kati,colincross/kati,colincross/kati,colincross/kati,danw/kati,colincross/kati,shinh/kati,danw/kati,google/kati,danw/kati,danw/kati,shinh/kati,shinh/kati,shinh/kati,danw/kati,shinh/kati,danw/kati