Run a check that Windows apps have no external dependencies.

It's relatively easy to accidentally include a binary that is linked against something *not* in the app bundle - especially if Python dependencies are compiled.

Briefcase should perform a check as part of the build (or maybe the packaging) process that the built binary is independent of non-app resources.

[This tool](https://lucasg.github.io/2018/04/29/Dependencies-command-line/) may be helpful.

Start by tracing Briefcase's Windows build and packaging process to find where a dependency check could run. Review the linked Dependencies tool for possible command-line usage; done means the build or packaging process detects binaries linked to resources outside the app bundle and reports the problem.

Written by the indexing model from the issue text.