How do I build openwebrtc on Raspberry PI 2?

I tried to build on Raspberry PI2 and it said this.

```
ubuntu@ubuntu:~/openwebrtc_work/cerbero$ ./cerbero-uninstalled -c config/linux.cbc fetch-package --full-reset --reset-rdeps openwebrtc
Traceback (most recent call last):
File "./cerbero-uninstalled", line 8, in
from cerbero.main import main
File "./cerbero/main.py", line 19, in
from cerbero import hacks
File "./cerbero/hacks.py", line 131, in
from cerbero.utils.shell import call
File "./cerbero/utils/shell.py", line 42, in
PLATFORM = system_info()[0]
File "./cerbero/utils/__init__.py", line 124, in system_info
raise FatalError(_("Architecture %s not supported") % arch)
cerbero.errors.FatalError: Fatal Error: Architecture armv7l not supported

```

What should I do now?

Reproduce the failure with ./cerbero-uninstalled -c config/linux.cbc fetch-package --full-reset --reset-rdeps openwebrtc on Raspberry Pi 2. Start in cerbero/utils/__init__.py at system_info(), where armv7l is rejected, and determine whether the supported build path should be documented or implemented; done means the Raspberry Pi 2 path is clear and the command proceeds.

Written by the indexing model from the issue text.