When a proguard config file is generated by some other target and referenced in proguard_config of an android_apk rule, an error similar to this one may appear.

ERROR Input to targets not generated by a dependency.
The file:
  //out/Debug/cronet/proguard_native.cfg
is listed as an input or source for the targets:
  //components/cronet/android:cronet_sample_apk__proguard
but this file was not generated by any dependencies of the targets. The target
that generates the file is:
  //components/cronet/android:cronet_combine_proguard_flags

This happens because the generated __proguard rule doesn't forward "deps" variable from the android_apk.