[FR] Raspberry Pi support

### [READ] For Firebase Unity SDK question, please report to [Firebase Unity Sample](https://github.com/firebase/quickstart-unity/issues/new/choose)

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### [REQUIRED] Please fill in the following fields:

* Pre-built SDK from the [website](https://firebase.google.com/download/cpp) or open-source from this repo: _____
* Firebase C++ SDK version: main
* Main Firebase Components in concern: Database (Auth, Database, etc.)
* Other Firebase Components in use: _____ (Auth, Database, etc.)
* Platform you are using the C++ SDK on: Arm Linux (raspberry Pi) (Mac, Windows, or Linux)
* Platform you are targeting: raspberry Pi (iOS, Android, and/or desktop)

### [REQUIRED] Please describe the question here:
Hi, I am trying to access database from raspberry pi running Linux (Armv7l). Can some one provide guide what changes need to be made for the c++ api to work on that?