Can't build Firebase via PodToBUILD/Bazel

### Step 0: Are you in the right place?

* For issues or feature requests related to __the code in this repository__
file a Github issue.
* If this is a __feature request__ please use the Feature Request template.
* For general technical questions, post a question on [StackOverflow](http://stackoverflow.com/)
with the `firebase` tag.
* For general (non-iOS) Firebase discussion, use the [firebase-talk](https://groups.google.com/forum/#!forum/firebase-talk)
google group.
* For backend issues, console issues, and other non-SDK help that does not fall under one
of the above categories, reach out to
[Firebase Support](https://firebase.google.com/support/).
* Once you've read this section and determined that your issue is appropriate for
this repository, please delete this section.

### [REQUIRED] Step 1: Describe your environment

* Xcode version: _11.6_
* Firebase SDK version: _6.28.2_
* Firebase Component: _N/A_ (Auth, Core, Database, Firestore, Messaging, Storage, etc)
* Component version: _N/A_
* Installation method: `CocoaPods`

### [REQUIRED] Step 2: Describe the problem

#### Steps to reproduce:

I am trying to build an iOS app with Firebase included, using PodToBUILD and Bazel. However, there doesn't seem to be an easy integration path, and mapping in pods according to PodToBUILD's docs cause a ton of issues.

Is there a sample project floating around somewhere, or a better integration path with Bazel that doesn't require CocoaPods? Could such an example be published, considering Bazel and Firebase are both part of Google's wider development efforts? :)

#### Relevant Code:

N/A