Fix(project template) Force bindings regen, if out dir empty.

[hdeshev]

Running tns build ... --bundle runs the clean gradle target and
we can end up deleting bindings *.dex files while the presence of
*.txt files in the generator dir will prevent us from regenerating
them.

The fix checks the output dir and forces regeneration if it has no
files.

[hdeshev]

Related to NativeScript/nativescript-cli#2110

[hdeshev]

Ping @Plamen5kov

[ns-bot]

💚

[petekanev]

Looks 👍 for invalidating the gradle's up-to-date status.

A definite fix to the problem with SBG not triggering when project's been cleared can be to output interfaces-names.txt, and potentially bindings.txt inside the project's build dir, or (build folder is cleaned on every prepare) make a custom generateBindings task. @Plamen5kov

[Plamen5kov]

@hdeshev I think a better solution would be to make our clean command take care of deleting the generated file in build-tools folder. That way we won't need additional logic to regenerate bindings. Maybe the template platforms/android/build.gradle can call the :asbg:clean command on the subproject. And the subproject can clean it's on generated files.

[hdeshev]

IMO the "right" solution to this problem is to generate all bindings-related .txt files inside the build/nativescript-bindings subfolder that will get properly cleaned and recreated.

I did a half-hearted attempt at getting that to run, but couldn't get it to work in reasonable time. Perhaps somebody who knows the gradle infrastructure better than me can have a shot.

[Plamen5kov]

I'll take a look.

[Plamen5kov]

closing in favor of: #598