Kernel snapshot input dependency tracking not working #147643

Haven't bisected this, but #147158 seems like the suspect.

Steps to reproduce:

flutter create -e test_1
cd test_1
flutter run -d macos

quit the application, modify the dart file

flutter run -d macos

Second run will not reflect modifications.

I'm guessing the problem is that after change the dart inputs are written into kernel_snapshot_program.stamp, while kernel_snapshot.stamp is empty, which causes the KernelSnapshot target (and thus the dependencies) skipped.

/cc @dcharkes, @christopherfujino